How do I use WPF bindings with RelativeSource

Question

How do I use RelativeSource with WPF bindings and what are the different use-cases

User · Answer

In WPF RelativeSource binding exposes three properties to set   1  Mode  This is an enum that could have four values      a  PreviousData value 0   It assigns the previous value of the property to   the bound one      b  TemplatedParent value 1    This is used when defining the templates of   any control and want to bind to a value Property of the control       For example  define ControlTemplate       lt ControlTemplate gt           lt CheckBox IsChecked   Binding RelativeSource  RelativeSource TemplatedParent   Path Value  Mode TwoWay  UpdateSourceTrigger PropertyChanged     gt    lt  ControlTemplate gt       c  Self value 2   When we want to bind from a self or a property of self       For example  Send checked state of checkbox as CommandParameter while setting the Command on CheckBox    lt CheckBox        CommandParameter   Binding RelativeSource  RelativeSource Self  Path IsChecked     gt       d  FindAncestor value 3   When want to bind from a parent control   in Visual Tree       For example  Bind a checkbox in records if a grid if header checkbox is checked    lt CheckBox IsChecked   Binding RelativeSource  RelativeSource Mode FindAncestor  AncestorType  x Type iDP XamDataGrid    Path DataContext IsHeaderChecked  Mode TwoWay     gt    2  AncestorType   when mode is FindAncestor then define what type of ancestor  RelativeSource  RelativeSource Mode FindAncestor  AncestorType  x Type iDP XamDataGrid     3  AncestorLevel   when mode is FindAncestor then what level of ancestor  if there are two same type of parent in visual tree   RelativeSource  RelativeSource Mode FindAncestor  AncestorType  x Type iDP XamDataGrid  AncestorLevel 1        Above are all use-cases for RelativeSource binding    Here is a reference link

User · Answer

Don t forget TemplatedParent    lt Binding RelativeSource   RelativeSource TemplatedParent    gt    or   Binding RelativeSource  RelativeSource TemplatedParent

User · Answer

I didn t read every answer  but I just want to add this information in case of relative source command binding of a button   When you use a relative source with Mode FindAncestor  the binding must be like   Command   Binding Path DataContext CommandProperty  RelativeSource           If you don t add DataContext in your path  at execution time it can t retrieve the property

User · Answer

Don t forget TemplatedParent    lt Binding RelativeSource   RelativeSource TemplatedParent    gt    or   Binding RelativeSource  RelativeSource TemplatedParent

User · Answer

If you want to bind to another property on the object    Binding Path PathToProperty  RelativeSource  RelativeSource Self     If you want to get a property on an ancestor    Binding Path PathToProperty      RelativeSource  RelativeSource AncestorType  x Type typeOfAncestor      If you want to get a property on the templated parent  so you can do 2 way bindings in a ControlTemplate    Binding Path PathToProperty  RelativeSource  RelativeSource TemplatedParent     or  shorter  this only works for OneWay bindings     TemplateBinding Path PathToProperty

User · Answer

This is an example of the use of this pattern that worked for me on empty datagrids    lt Style Triggers gt       lt DataTrigger Binding   Binding Items Count  RelativeSource  RelativeSource Self    Value  0  gt           lt Setter Property  Background  gt               lt Setter Value gt                   lt VisualBrush Stretch  None  gt                       lt VisualBrush Visual gt                           lt TextBlock Text  We did t find any matching records for your search     FontSize  16  FontWeight  SemiBold  Foreground  LightCoral   gt                       lt  VisualBrush Visual gt                   lt  VisualBrush gt               lt  Setter Value gt           lt  Setter gt       lt  DataTrigger gt   lt  Style Triggers gt

User · Answer

In WPF RelativeSource binding exposes three properties to set   1  Mode  This is an enum that could have four values      a  PreviousData value 0   It assigns the previous value of the property to   the bound one      b  TemplatedParent value 1    This is used when defining the templates of   any control and want to bind to a value Property of the control       For example  define ControlTemplate       lt ControlTemplate gt           lt CheckBox IsChecked   Binding RelativeSource  RelativeSource TemplatedParent   Path Value  Mode TwoWay  UpdateSourceTrigger PropertyChanged     gt    lt  ControlTemplate gt       c  Self value 2   When we want to bind from a self or a property of self       For example  Send checked state of checkbox as CommandParameter while setting the Command on CheckBox    lt CheckBox        CommandParameter   Binding RelativeSource  RelativeSource Self  Path IsChecked     gt       d  FindAncestor value 3   When want to bind from a parent control   in Visual Tree       For example  Bind a checkbox in records if a grid if header checkbox is checked    lt CheckBox IsChecked   Binding RelativeSource  RelativeSource Mode FindAncestor  AncestorType  x Type iDP XamDataGrid    Path DataContext IsHeaderChecked  Mode TwoWay     gt    2  AncestorType   when mode is FindAncestor then define what type of ancestor  RelativeSource  RelativeSource Mode FindAncestor  AncestorType  x Type iDP XamDataGrid     3  AncestorLevel   when mode is FindAncestor then what level of ancestor  if there are two same type of parent in visual tree   RelativeSource  RelativeSource Mode FindAncestor  AncestorType  x Type iDP XamDataGrid  AncestorLevel 1        Above are all use-cases for RelativeSource binding    Here is a reference link

User · Answer

I just posted another solution for accessing the DataContext of a parent element in Silverlight that works for me  It uses Binding ElementName

User · Answer

Binding RelativeSource       RelativeSource Mode FindAncestor  AncestorType  x Type ItemType          The default attribute of RelativeSource is the Mode property   A complete set of valid values is given here  from MSDN     PreviousData Allows you to bind the previous data item  not that control that contains the data item  in the list of data items being displayed  TemplatedParent Refers to the element to which the template  in which the data-bound element exists  is applied  This is similar to setting a TemplateBindingExtension and is only applicable if the Binding is within a template  Self Refers to the element on which you are setting the binding and allows you to bind one property of that element to another property on the same element  FindAncestor Refers to the ancestor in the parent chain of the data-bound element  You can use this to bind to an ancestor of a specific type or its subclasses  This is the mode you use if you want to specify AncestorType and or AncestorLevel

User · Answer

Binding RelativeSource       RelativeSource Mode FindAncestor  AncestorType  x Type ItemType          The default attribute of RelativeSource is the Mode property   A complete set of valid values is given here  from MSDN     PreviousData Allows you to bind the previous data item  not that control that contains the data item  in the list of data items being displayed  TemplatedParent Refers to the element to which the template  in which the data-bound element exists  is applied  This is similar to setting a TemplateBindingExtension and is only applicable if the Binding is within a template  Self Refers to the element on which you are setting the binding and allows you to bind one property of that element to another property on the same element  FindAncestor Refers to the ancestor in the parent chain of the data-bound element  You can use this to bind to an ancestor of a specific type or its subclasses  This is the mode you use if you want to specify AncestorType and or AncestorLevel

User · Answer

I didn t read every answer  but I just want to add this information in case of relative source command binding of a button   When you use a relative source with Mode FindAncestor  the binding must be like   Command   Binding Path DataContext CommandProperty  RelativeSource           If you don t add DataContext in your path  at execution time it can t retrieve the property

User · Answer

Binding RelativeSource       RelativeSource Mode FindAncestor  AncestorType  x Type ItemType          The default attribute of RelativeSource is the Mode property   A complete set of valid values is given here  from MSDN     PreviousData Allows you to bind the previous data item  not that control that contains the data item  in the list of data items being displayed  TemplatedParent Refers to the element to which the template  in which the data-bound element exists  is applied  This is similar to setting a TemplateBindingExtension and is only applicable if the Binding is within a template  Self Refers to the element on which you are setting the binding and allows you to bind one property of that element to another property on the same element  FindAncestor Refers to the ancestor in the parent chain of the data-bound element  You can use this to bind to an ancestor of a specific type or its subclasses  This is the mode you use if you want to specify AncestorType and or AncestorLevel

User · Answer

I just posted another solution for accessing the DataContext of a parent element in Silverlight that works for me  It uses Binding ElementName

User · Answer

Don t forget TemplatedParent    lt Binding RelativeSource   RelativeSource TemplatedParent    gt    or   Binding RelativeSource  RelativeSource TemplatedParent

User · Answer

I created a library to simplify the binding syntax of WPF including making it easier to use RelativeSource  Here are some examples  Before    Binding Path PathToProperty  RelativeSource  RelativeSource Self    Binding Path PathToProperty  RelativeSource  RelativeSource AncestorType  x Type typeOfAncestor     Binding Path PathToProperty  RelativeSource  RelativeSource TemplatedParent    Binding Path Text  ElementName MyTextBox    After    BindTo PathToProperty   BindTo Ancestor typeOfAncestor PathToProperty   BindTo Template PathToProperty   BindTo  MyTextBox Text    Here is an example of how method binding is simplified  Before      C  code private ICommand  saveCommand  public ICommand SaveCommand    get     if   saveCommand    null        saveCommand   new RelayCommand x   gt  this SaveObject           return  saveCommand        private void SaveObject         do something       XAML  Binding Path SaveCommand    After      C  code private void SaveObject         do something       XAML  BindTo SaveObject      You can find the library here  http   www simplygoodcode com 2012 08 simpler-wpf-binding html  Note in the  BEFORE  example that I use for method binding that code was already optimized by using RelayCommand which last I checked is not a native part of WPF  Without that the  BEFORE  example would have been even longer

User · Answer

It s worthy of note that for those stumbling across this thinking of Silverlight   Silverlight offers a reduced subset only  of these commands

User · Answer

I just posted another solution for accessing the DataContext of a parent element in Silverlight that works for me  It uses Binding ElementName

User · Answer

Don t forget TemplatedParent    lt Binding RelativeSource   RelativeSource TemplatedParent    gt    or   Binding RelativeSource  RelativeSource TemplatedParent

User · Answer

If an element is not part of the visual tree  then RelativeSource will never work  In this case  you need to try a different technique  pioneered by Thomas Levesque  He has the solution on his blog under  WPF  How to bind to data when the DataContext is not inherited  And it works absolutely brilliantly  In the unlikely event that his blog is down  Appendix A contains a mirror copy of his article  Please do not comment here  please comment directly on his blog post  Appendix A  Mirror of blog post The DataContext property in WPF is extremely handy  because it is automatically inherited by all children of the element where you assign it  therefore you don   t need to set it again on each element you want to bind  However  in some cases the DataContext is not accessible  it happens for elements that are not part of the visual or logical tree  It can be very difficult then to bind a property on those elements    Let   s illustrate with a simple example  we want to display a list of products in a DataGrid  In the grid  we want to be able to show or hide the Price column  based on the value of a ShowPrice property exposed by the ViewModel  The obvious approach is to bind the Visibility of the column to the ShowPrice property   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding ShowPrice                  Converter  StaticResource visibilityConverter   quot   gt   Unfortunately  changing the value of ShowPrice has no effect  and the column is always visible    why  If we look at the Output window in Visual Studio  we notice the following line   System Windows Data Error  2   Cannot find governing FrameworkElement or FrameworkContentElement for target element  BindingExpression Path ShowPrice  DataItem null  target element is    DataGridTextColumn     HashCode 32685253   target property is    Visibility     type    Visibility     The message is rather cryptic  but the meaning is actually quite simple  WPF doesn   t know which FrameworkElement to use to get the DataContext  because the column doesn   t belong to the visual or logical tree of the DataGrid   We can try to tweak the binding to get the desired result  for instance by setting the RelativeSource to the DataGrid itself   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding DataContext ShowPrice                  Converter  StaticResource visibilityConverter                   RelativeSource  RelativeSource FindAncestor  AncestorType DataGrid   quot   gt   Or we can add a CheckBox bound to ShowPrice  and try to bind the column visibility to the IsChecked property by specifying the element name   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding IsChecked                  Converter  StaticResource visibilityConverter                   ElementName chkShowPrice  quot   gt   But none of these workarounds seems to work  we always get the same result    At this point  it seems that the only viable approach would be to change the column visibility in code-behind  which we usually prefer to avoid when using the MVVM pattern    But I   m not going to give up so soon  at least not while there are other options to consider  The solution to our problem is actually quite simple  and takes advantage of the Freezable class  The primary purpose of this class is to define objects that have a modifiable and a read-only state  but the interesting feature in our case is that Freezable objects can inherit the DataContext even when they   re not in the visual or logical tree  I don   t know the exact mechanism that enables this behavior  but we   re going to take advantage of it to make our binding work    The idea is to create a class  I called it BindingProxy for reasons that should become obvious very soon  that inherits Freezable and declares a Data dependency property  public class BindingProxy   Freezable        region Overrides of Freezable       protected override Freezable CreateInstanceCore                 return new BindingProxy                 endregion       public object Data               get   return  object GetValue DataProperty             set   SetValue DataProperty  value                    Using a DependencyProperty as the backing store for Data   This enables animation  styling  binding  etc        public static readonly DependencyProperty DataProperty           DependencyProperty Register  quot Data quot   typeof object   typeof BindingProxy   new UIPropertyMetadata null       We can then declare an instance of this class in the resources of the DataGrid  and bind the Data property to the current DataContext   lt DataGrid Resources gt       lt local BindingProxy x Key  quot proxy quot  Data  quot  Binding  quot    gt   lt  DataGrid Resources gt   The last step is to specify this BindingProxy object  easily accessible with StaticResource  as the Source for the binding   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding Data ShowPrice                  Converter  StaticResource visibilityConverter                   Source  StaticResource proxy   quot   gt   Note that the binding path has been prefixed with    Data     since the path is now relative to the BindingProxy object  The binding now works correctly  and the column is properly shown or hidden based on the ShowPrice property

User · Answer

If you want to bind to another property on the object    Binding Path PathToProperty  RelativeSource  RelativeSource Self     If you want to get a property on an ancestor    Binding Path PathToProperty      RelativeSource  RelativeSource AncestorType  x Type typeOfAncestor      If you want to get a property on the templated parent  so you can do 2 way bindings in a ControlTemplate    Binding Path PathToProperty  RelativeSource  RelativeSource TemplatedParent     or  shorter  this only works for OneWay bindings     TemplateBinding Path PathToProperty

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Here s a more visual explanation in the context of a MVVM architecture

User · Answer

If you want to bind to another property on the object    Binding Path PathToProperty  RelativeSource  RelativeSource Self     If you want to get a property on an ancestor    Binding Path PathToProperty      RelativeSource  RelativeSource AncestorType  x Type typeOfAncestor      If you want to get a property on the templated parent  so you can do 2 way bindings in a ControlTemplate    Binding Path PathToProperty  RelativeSource  RelativeSource TemplatedParent     or  shorter  this only works for OneWay bindings     TemplateBinding Path PathToProperty

User · Answer

Some useful bits and pieces   Here s how to do it mostly in code   Binding b   new Binding    b RelativeSource   new RelativeSource RelativeSourceMode FindAncestor  this GetType    1   b Path   new PropertyPath  MyElementThatNeedsBinding    MyLabel SetBinding ContentProperty  b     I largely copied this from Binding Relative Source in code Behind   Also  the MSDN page is pretty good as far as examples go  RelativeSource Class

User · Answer

If you want to bind to another property on the object    Binding Path PathToProperty  RelativeSource  RelativeSource Self     If you want to get a property on an ancestor    Binding Path PathToProperty      RelativeSource  RelativeSource AncestorType  x Type typeOfAncestor      If you want to get a property on the templated parent  so you can do 2 way bindings in a ControlTemplate    Binding Path PathToProperty  RelativeSource  RelativeSource TemplatedParent     or  shorter  this only works for OneWay bindings     TemplateBinding Path PathToProperty

User · Answer

It s worthy of note that for those stumbling across this thinking of Silverlight   Silverlight offers a reduced subset only  of these commands

User · Answer

This is an example of the use of this pattern that worked for me on empty datagrids    lt Style Triggers gt       lt DataTrigger Binding   Binding Items Count  RelativeSource  RelativeSource Self    Value  0  gt           lt Setter Property  Background  gt               lt Setter Value gt                   lt VisualBrush Stretch  None  gt                       lt VisualBrush Visual gt                           lt TextBlock Text  We did t find any matching records for your search     FontSize  16  FontWeight  SemiBold  Foreground  LightCoral   gt                       lt  VisualBrush Visual gt                   lt  VisualBrush gt               lt  Setter Value gt           lt  Setter gt       lt  DataTrigger gt   lt  Style Triggers gt

User · Answer

Bechir Bejaoui exposes the use cases of the RelativeSources in WPF in his article here      The RelativeSource is a markup extension that is used in particular   binding cases when we try to bind a property of a given object to   another property of the object itself  when we try to bind a property   of a object to another one of its relative parents  when binding a   dependency property value to a piece of XAML in case of custom control   development and finally in case of using a differential of a series of   a bound data  All of those situations are expressed as relative source   modes  I will expose all of those cases one by one          Mode Self          Imagine this case  a rectangle that we want that its height is always   equal to its width  a square let s say  We can do this using the   element name   lt Rectangle Fill  Red  Name  rectangle                   Height  100  Stroke  Black                   Canvas Top  100  Canvas Left  100                  Width   Binding ElementName rectangle                  Path Height    gt        But in this above case we are obliged to indicate the name of the   binding object  namely the rectangle  We can reach the same purpose   differently using the RelativeSource    lt Rectangle Fill  Red  Height  100                  Stroke  Black                  Width   Binding RelativeSource  RelativeSource Self                  Path Height    gt        For that case we are not obliged to mention the name of the binding   object and the Width will be always equal to the Height whenever the   height is changed        If you want to parameter the Width to be the half of the height then   you can do this by adding a converter to the Binding markup extension    Let s imagine another case now     lt TextBlock Width   Binding RelativeSource  RelativeSource Self                  Path Parent ActualWidth    gt        The above case is used to tie a given property of a given element to   one of its direct parent ones as this element holds a property that is   called Parent  This leads us to another relative source mode which is   the FindAncestor one           Mode FindAncestor         In this case  a property of a given element will be tied to one of its   parents  Of Corse  The main difference with the above case is the fact   that  it s up to you to determine the ancestor type and the ancestor   rank in the hierarchy to tie the property  By the way try to play with   this piece of XAML   lt Canvas Name  Parent0  gt       lt Border Name  Parent1               Width   Binding RelativeSource  RelativeSource Self                Path Parent ActualWidth                Height   Binding RelativeSource  RelativeSource Self                Path Parent ActualHeight   gt           lt Canvas Name  Parent2  gt               lt Border Name  Parent3              Width   Binding RelativeSource  RelativeSource Self              Path Parent ActualWidth              Height   Binding RelativeSource  RelativeSource Self                 Path Parent ActualHeight   gt                  lt Canvas Name  Parent4  gt                  lt TextBlock FontSize  16                  Margin  5  Text  Display the name of the ancestor   gt                  lt TextBlock FontSize  16                    Margin  50               Text   Binding RelativeSource  RelativeSource                          FindAncestor                         AncestorType  x Type Border                           AncestorLevel 2  Path Name                           Width  200   gt                   lt  Canvas gt               lt  Border gt           lt  Canvas gt        lt  Border gt      lt  Canvas gt        The above situation is of two TextBlock elements those are embedded   within a series of borders and canvas elements those represent their   hierarchical parents  The second TextBlock will display the name of   the given parent at the relative source level       So try to change AncestorLevel 2 to AncestorLevel 1 and see what   happens  Then try to change the type of the ancestor from   AncestorType Border to AncestorType Canvas and see what s happens        The displayed text will change according to the Ancestor type and   level  Then what s happen if the ancestor level is not suitable to the   ancestor type  This is a good question  I know that you re about to   ask it  The response is no exceptions will be thrown and nothings will   be displayed at the TextBlock level           TemplatedParent         This mode enables tie a given ControlTemplate property to a property   of the control that the ControlTemplate is applied to  To well   understand the issue here is an example bellow   lt Window Resources gt   lt ControlTemplate x Key  template  gt           lt Canvas gt               lt Canvas RenderTransform gt                   lt RotateTransform Angle  20   gt                   lt  Canvas RenderTransform gt               lt Ellipse Height  100  Width  150                    Fill   Binding              RelativeSource  RelativeSource TemplatedParent               Path Background   gt                  lt  Ellipse gt               lt ContentPresenter Margin  35                     Content   Binding RelativeSource  RelativeSource                     TemplatedParent  Path Content    gt           lt  Canvas gt       lt  ControlTemplate gt   lt  Window Resources gt       lt Canvas Name  Parent0  gt       lt Button   Margin  50                 Template   StaticResource template   Height  0                 Canvas Left  0  Canvas Top  0  Width  0  gt           lt TextBlock FontSize  22  gt Click me lt  TextBlock gt       lt  Button gt    lt  Canvas gt        If I want to apply the properties of a given control to its control   template then I can use the TemplatedParent mode  There is also a   similar one to this markup extension which is the TemplateBinding   which is a kind of short hand of the first one  but the   TemplateBinding is evaluated at compile time at the contrast of the   TemplatedParent which is evaluated just after the first run time  As   you can remark in the bellow figure  the background and the content   are applied from within the button to the control template

User · Answer

Don t forget TemplatedParent    lt Binding RelativeSource   RelativeSource TemplatedParent    gt    or   Binding RelativeSource  RelativeSource TemplatedParent

User · Answer

Don t forget TemplatedParent    lt Binding RelativeSource   RelativeSource TemplatedParent    gt    or   Binding RelativeSource  RelativeSource TemplatedParent

User · Answer

I didn t read every answer  but I just want to add this information in case of relative source command binding of a button   When you use a relative source with Mode FindAncestor  the binding must be like   Command   Binding Path DataContext CommandProperty  RelativeSource           If you don t add DataContext in your path  at execution time it can t retrieve the property

User · Answer

In WPF RelativeSource binding exposes three properties to set   1  Mode  This is an enum that could have four values      a  PreviousData value 0   It assigns the previous value of the property to   the bound one      b  TemplatedParent value 1    This is used when defining the templates of   any control and want to bind to a value Property of the control       For example  define ControlTemplate       lt ControlTemplate gt           lt CheckBox IsChecked   Binding RelativeSource  RelativeSource TemplatedParent   Path Value  Mode TwoWay  UpdateSourceTrigger PropertyChanged     gt    lt  ControlTemplate gt       c  Self value 2   When we want to bind from a self or a property of self       For example  Send checked state of checkbox as CommandParameter while setting the Command on CheckBox    lt CheckBox        CommandParameter   Binding RelativeSource  RelativeSource Self  Path IsChecked     gt       d  FindAncestor value 3   When want to bind from a parent control   in Visual Tree       For example  Bind a checkbox in records if a grid if header checkbox is checked    lt CheckBox IsChecked   Binding RelativeSource  RelativeSource Mode FindAncestor  AncestorType  x Type iDP XamDataGrid    Path DataContext IsHeaderChecked  Mode TwoWay     gt    2  AncestorType   when mode is FindAncestor then define what type of ancestor  RelativeSource  RelativeSource Mode FindAncestor  AncestorType  x Type iDP XamDataGrid     3  AncestorLevel   when mode is FindAncestor then what level of ancestor  if there are two same type of parent in visual tree   RelativeSource  RelativeSource Mode FindAncestor  AncestorType  x Type iDP XamDataGrid  AncestorLevel 1        Above are all use-cases for RelativeSource binding    Here is a reference link

User · Answer

Don t forget TemplatedParent    lt Binding RelativeSource   RelativeSource TemplatedParent    gt    or   Binding RelativeSource  RelativeSource TemplatedParent

User · Answer

If an element is not part of the visual tree  then RelativeSource will never work  In this case  you need to try a different technique  pioneered by Thomas Levesque  He has the solution on his blog under  WPF  How to bind to data when the DataContext is not inherited  And it works absolutely brilliantly  In the unlikely event that his blog is down  Appendix A contains a mirror copy of his article  Please do not comment here  please comment directly on his blog post  Appendix A  Mirror of blog post The DataContext property in WPF is extremely handy  because it is automatically inherited by all children of the element where you assign it  therefore you don   t need to set it again on each element you want to bind  However  in some cases the DataContext is not accessible  it happens for elements that are not part of the visual or logical tree  It can be very difficult then to bind a property on those elements    Let   s illustrate with a simple example  we want to display a list of products in a DataGrid  In the grid  we want to be able to show or hide the Price column  based on the value of a ShowPrice property exposed by the ViewModel  The obvious approach is to bind the Visibility of the column to the ShowPrice property   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding ShowPrice                  Converter  StaticResource visibilityConverter   quot   gt   Unfortunately  changing the value of ShowPrice has no effect  and the column is always visible    why  If we look at the Output window in Visual Studio  we notice the following line   System Windows Data Error  2   Cannot find governing FrameworkElement or FrameworkContentElement for target element  BindingExpression Path ShowPrice  DataItem null  target element is    DataGridTextColumn     HashCode 32685253   target property is    Visibility     type    Visibility     The message is rather cryptic  but the meaning is actually quite simple  WPF doesn   t know which FrameworkElement to use to get the DataContext  because the column doesn   t belong to the visual or logical tree of the DataGrid   We can try to tweak the binding to get the desired result  for instance by setting the RelativeSource to the DataGrid itself   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding DataContext ShowPrice                  Converter  StaticResource visibilityConverter                   RelativeSource  RelativeSource FindAncestor  AncestorType DataGrid   quot   gt   Or we can add a CheckBox bound to ShowPrice  and try to bind the column visibility to the IsChecked property by specifying the element name   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding IsChecked                  Converter  StaticResource visibilityConverter                   ElementName chkShowPrice  quot   gt   But none of these workarounds seems to work  we always get the same result    At this point  it seems that the only viable approach would be to change the column visibility in code-behind  which we usually prefer to avoid when using the MVVM pattern    But I   m not going to give up so soon  at least not while there are other options to consider  The solution to our problem is actually quite simple  and takes advantage of the Freezable class  The primary purpose of this class is to define objects that have a modifiable and a read-only state  but the interesting feature in our case is that Freezable objects can inherit the DataContext even when they   re not in the visual or logical tree  I don   t know the exact mechanism that enables this behavior  but we   re going to take advantage of it to make our binding work    The idea is to create a class  I called it BindingProxy for reasons that should become obvious very soon  that inherits Freezable and declares a Data dependency property  public class BindingProxy   Freezable        region Overrides of Freezable       protected override Freezable CreateInstanceCore                 return new BindingProxy                 endregion       public object Data               get   return  object GetValue DataProperty             set   SetValue DataProperty  value                    Using a DependencyProperty as the backing store for Data   This enables animation  styling  binding  etc        public static readonly DependencyProperty DataProperty           DependencyProperty Register  quot Data quot   typeof object   typeof BindingProxy   new UIPropertyMetadata null       We can then declare an instance of this class in the resources of the DataGrid  and bind the Data property to the current DataContext   lt DataGrid Resources gt       lt local BindingProxy x Key  quot proxy quot  Data  quot  Binding  quot    gt   lt  DataGrid Resources gt   The last step is to specify this BindingProxy object  easily accessible with StaticResource  as the Source for the binding   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding Data ShowPrice                  Converter  StaticResource visibilityConverter                   Source  StaticResource proxy   quot   gt   Note that the binding path has been prefixed with    Data     since the path is now relative to the BindingProxy object  The binding now works correctly  and the column is properly shown or hidden based on the ShowPrice property

User · Answer

Bechir Bejaoui exposes the use cases of the RelativeSources in WPF in his article here      The RelativeSource is a markup extension that is used in particular   binding cases when we try to bind a property of a given object to   another property of the object itself  when we try to bind a property   of a object to another one of its relative parents  when binding a   dependency property value to a piece of XAML in case of custom control   development and finally in case of using a differential of a series of   a bound data  All of those situations are expressed as relative source   modes  I will expose all of those cases one by one          Mode Self          Imagine this case  a rectangle that we want that its height is always   equal to its width  a square let s say  We can do this using the   element name   lt Rectangle Fill  Red  Name  rectangle                   Height  100  Stroke  Black                   Canvas Top  100  Canvas Left  100                  Width   Binding ElementName rectangle                  Path Height    gt        But in this above case we are obliged to indicate the name of the   binding object  namely the rectangle  We can reach the same purpose   differently using the RelativeSource    lt Rectangle Fill  Red  Height  100                  Stroke  Black                  Width   Binding RelativeSource  RelativeSource Self                  Path Height    gt        For that case we are not obliged to mention the name of the binding   object and the Width will be always equal to the Height whenever the   height is changed        If you want to parameter the Width to be the half of the height then   you can do this by adding a converter to the Binding markup extension    Let s imagine another case now     lt TextBlock Width   Binding RelativeSource  RelativeSource Self                  Path Parent ActualWidth    gt        The above case is used to tie a given property of a given element to   one of its direct parent ones as this element holds a property that is   called Parent  This leads us to another relative source mode which is   the FindAncestor one           Mode FindAncestor         In this case  a property of a given element will be tied to one of its   parents  Of Corse  The main difference with the above case is the fact   that  it s up to you to determine the ancestor type and the ancestor   rank in the hierarchy to tie the property  By the way try to play with   this piece of XAML   lt Canvas Name  Parent0  gt       lt Border Name  Parent1               Width   Binding RelativeSource  RelativeSource Self                Path Parent ActualWidth                Height   Binding RelativeSource  RelativeSource Self                Path Parent ActualHeight   gt           lt Canvas Name  Parent2  gt               lt Border Name  Parent3              Width   Binding RelativeSource  RelativeSource Self              Path Parent ActualWidth              Height   Binding RelativeSource  RelativeSource Self                 Path Parent ActualHeight   gt                  lt Canvas Name  Parent4  gt                  lt TextBlock FontSize  16                  Margin  5  Text  Display the name of the ancestor   gt                  lt TextBlock FontSize  16                    Margin  50               Text   Binding RelativeSource  RelativeSource                          FindAncestor                         AncestorType  x Type Border                           AncestorLevel 2  Path Name                           Width  200   gt                   lt  Canvas gt               lt  Border gt           lt  Canvas gt        lt  Border gt      lt  Canvas gt        The above situation is of two TextBlock elements those are embedded   within a series of borders and canvas elements those represent their   hierarchical parents  The second TextBlock will display the name of   the given parent at the relative source level       So try to change AncestorLevel 2 to AncestorLevel 1 and see what   happens  Then try to change the type of the ancestor from   AncestorType Border to AncestorType Canvas and see what s happens        The displayed text will change according to the Ancestor type and   level  Then what s happen if the ancestor level is not suitable to the   ancestor type  This is a good question  I know that you re about to   ask it  The response is no exceptions will be thrown and nothings will   be displayed at the TextBlock level           TemplatedParent         This mode enables tie a given ControlTemplate property to a property   of the control that the ControlTemplate is applied to  To well   understand the issue here is an example bellow   lt Window Resources gt   lt ControlTemplate x Key  template  gt           lt Canvas gt               lt Canvas RenderTransform gt                   lt RotateTransform Angle  20   gt                   lt  Canvas RenderTransform gt               lt Ellipse Height  100  Width  150                    Fill   Binding              RelativeSource  RelativeSource TemplatedParent               Path Background   gt                  lt  Ellipse gt               lt ContentPresenter Margin  35                     Content   Binding RelativeSource  RelativeSource                     TemplatedParent  Path Content    gt           lt  Canvas gt       lt  ControlTemplate gt   lt  Window Resources gt       lt Canvas Name  Parent0  gt       lt Button   Margin  50                 Template   StaticResource template   Height  0                 Canvas Left  0  Canvas Top  0  Width  0  gt           lt TextBlock FontSize  22  gt Click me lt  TextBlock gt       lt  Button gt    lt  Canvas gt        If I want to apply the properties of a given control to its control   template then I can use the TemplatedParent mode  There is also a   similar one to this markup extension which is the TemplateBinding   which is a kind of short hand of the first one  but the   TemplateBinding is evaluated at compile time at the contrast of the   TemplatedParent which is evaluated just after the first run time  As   you can remark in the bellow figure  the background and the content   are applied from within the button to the control template

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Binding RelativeSource       RelativeSource Mode FindAncestor  AncestorType  x Type ItemType          The default attribute of RelativeSource is the Mode property   A complete set of valid values is given here  from MSDN     PreviousData Allows you to bind the previous data item  not that control that contains the data item  in the list of data items being displayed  TemplatedParent Refers to the element to which the template  in which the data-bound element exists  is applied  This is similar to setting a TemplateBindingExtension and is only applicable if the Binding is within a template  Self Refers to the element on which you are setting the binding and allows you to bind one property of that element to another property on the same element  FindAncestor Refers to the ancestor in the parent chain of the data-bound element  You can use this to bind to an ancestor of a specific type or its subclasses  This is the mode you use if you want to specify AncestorType and or AncestorLevel

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It s worthy of note that for those stumbling across this thinking of Silverlight   Silverlight offers a reduced subset only  of these commands

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Here s a more visual explanation in the context of a MVVM architecture

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This is an example of the use of this pattern that worked for me on empty datagrids    lt Style Triggers gt       lt DataTrigger Binding   Binding Items Count  RelativeSource  RelativeSource Self    Value  0  gt           lt Setter Property  Background  gt               lt Setter Value gt                   lt VisualBrush Stretch  None  gt                       lt VisualBrush Visual gt                           lt TextBlock Text  We did t find any matching records for your search     FontSize  16  FontWeight  SemiBold  Foreground  LightCoral   gt                       lt  VisualBrush Visual gt                   lt  VisualBrush gt               lt  Setter Value gt           lt  Setter gt       lt  DataTrigger gt   lt  Style Triggers gt

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It s worthy of note that for those stumbling across this thinking of Silverlight   Silverlight offers a reduced subset only  of these commands

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If you want to bind to another property on the object    Binding Path PathToProperty  RelativeSource  RelativeSource Self     If you want to get a property on an ancestor    Binding Path PathToProperty      RelativeSource  RelativeSource AncestorType  x Type typeOfAncestor      If you want to get a property on the templated parent  so you can do 2 way bindings in a ControlTemplate    Binding Path PathToProperty  RelativeSource  RelativeSource TemplatedParent     or  shorter  this only works for OneWay bindings     TemplateBinding Path PathToProperty

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I didn t read every answer  but I just want to add this information in case of relative source command binding of a button   When you use a relative source with Mode FindAncestor  the binding must be like   Command   Binding Path DataContext CommandProperty  RelativeSource           If you don t add DataContext in your path  at execution time it can t retrieve the property

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I created a library to simplify the binding syntax of WPF including making it easier to use RelativeSource  Here are some examples  Before    Binding Path PathToProperty  RelativeSource  RelativeSource Self    Binding Path PathToProperty  RelativeSource  RelativeSource AncestorType  x Type typeOfAncestor     Binding Path PathToProperty  RelativeSource  RelativeSource TemplatedParent    Binding Path Text  ElementName MyTextBox    After    BindTo PathToProperty   BindTo Ancestor typeOfAncestor PathToProperty   BindTo Template PathToProperty   BindTo  MyTextBox Text    Here is an example of how method binding is simplified  Before      C  code private ICommand  saveCommand  public ICommand SaveCommand    get     if   saveCommand    null        saveCommand   new RelayCommand x   gt  this SaveObject           return  saveCommand        private void SaveObject         do something       XAML  Binding Path SaveCommand    After      C  code private void SaveObject         do something       XAML  BindTo SaveObject      You can find the library here  http   www simplygoodcode com 2012 08 simpler-wpf-binding html  Note in the  BEFORE  example that I use for method binding that code was already optimized by using RelayCommand which last I checked is not a native part of WPF  Without that the  BEFORE  example would have been even longer

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In WPF RelativeSource binding exposes three properties to set   1  Mode  This is an enum that could have four values      a  PreviousData value 0   It assigns the previous value of the property to   the bound one      b  TemplatedParent value 1    This is used when defining the templates of   any control and want to bind to a value Property of the control       For example  define ControlTemplate       lt ControlTemplate gt           lt CheckBox IsChecked   Binding RelativeSource  RelativeSource TemplatedParent   Path Value  Mode TwoWay  UpdateSourceTrigger PropertyChanged     gt    lt  ControlTemplate gt       c  Self value 2   When we want to bind from a self or a property of self       For example  Send checked state of checkbox as CommandParameter while setting the Command on CheckBox    lt CheckBox        CommandParameter   Binding RelativeSource  RelativeSource Self  Path IsChecked     gt       d  FindAncestor value 3   When want to bind from a parent control   in Visual Tree       For example  Bind a checkbox in records if a grid if header checkbox is checked    lt CheckBox IsChecked   Binding RelativeSource  RelativeSource Mode FindAncestor  AncestorType  x Type iDP XamDataGrid    Path DataContext IsHeaderChecked  Mode TwoWay     gt    2  AncestorType   when mode is FindAncestor then define what type of ancestor  RelativeSource  RelativeSource Mode FindAncestor  AncestorType  x Type iDP XamDataGrid     3  AncestorLevel   when mode is FindAncestor then what level of ancestor  if there are two same type of parent in visual tree   RelativeSource  RelativeSource Mode FindAncestor  AncestorType  x Type iDP XamDataGrid  AncestorLevel 1        Above are all use-cases for RelativeSource binding    Here is a reference link

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If you want to bind to another property on the object    Binding Path PathToProperty  RelativeSource  RelativeSource Self     If you want to get a property on an ancestor    Binding Path PathToProperty      RelativeSource  RelativeSource AncestorType  x Type typeOfAncestor      If you want to get a property on the templated parent  so you can do 2 way bindings in a ControlTemplate    Binding Path PathToProperty  RelativeSource  RelativeSource TemplatedParent     or  shorter  this only works for OneWay bindings     TemplateBinding Path PathToProperty

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This is an example of the use of this pattern that worked for me on empty datagrids    lt Style Triggers gt       lt DataTrigger Binding   Binding Items Count  RelativeSource  RelativeSource Self    Value  0  gt           lt Setter Property  Background  gt               lt Setter Value gt                   lt VisualBrush Stretch  None  gt                       lt VisualBrush Visual gt                           lt TextBlock Text  We did t find any matching records for your search     FontSize  16  FontWeight  SemiBold  Foreground  LightCoral   gt                       lt  VisualBrush Visual gt                   lt  VisualBrush gt               lt  Setter Value gt           lt  Setter gt       lt  DataTrigger gt   lt  Style Triggers gt

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I just posted another solution for accessing the DataContext of a parent element in Silverlight that works for me  It uses Binding ElementName

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Bechir Bejaoui exposes the use cases of the RelativeSources in WPF in his article here      The RelativeSource is a markup extension that is used in particular   binding cases when we try to bind a property of a given object to   another property of the object itself  when we try to bind a property   of a object to another one of its relative parents  when binding a   dependency property value to a piece of XAML in case of custom control   development and finally in case of using a differential of a series of   a bound data  All of those situations are expressed as relative source   modes  I will expose all of those cases one by one          Mode Self          Imagine this case  a rectangle that we want that its height is always   equal to its width  a square let s say  We can do this using the   element name   lt Rectangle Fill  Red  Name  rectangle                   Height  100  Stroke  Black                   Canvas Top  100  Canvas Left  100                  Width   Binding ElementName rectangle                  Path Height    gt        But in this above case we are obliged to indicate the name of the   binding object  namely the rectangle  We can reach the same purpose   differently using the RelativeSource    lt Rectangle Fill  Red  Height  100                  Stroke  Black                  Width   Binding RelativeSource  RelativeSource Self                  Path Height    gt        For that case we are not obliged to mention the name of the binding   object and the Width will be always equal to the Height whenever the   height is changed        If you want to parameter the Width to be the half of the height then   you can do this by adding a converter to the Binding markup extension    Let s imagine another case now     lt TextBlock Width   Binding RelativeSource  RelativeSource Self                  Path Parent ActualWidth    gt        The above case is used to tie a given property of a given element to   one of its direct parent ones as this element holds a property that is   called Parent  This leads us to another relative source mode which is   the FindAncestor one           Mode FindAncestor         In this case  a property of a given element will be tied to one of its   parents  Of Corse  The main difference with the above case is the fact   that  it s up to you to determine the ancestor type and the ancestor   rank in the hierarchy to tie the property  By the way try to play with   this piece of XAML   lt Canvas Name  Parent0  gt       lt Border Name  Parent1               Width   Binding RelativeSource  RelativeSource Self                Path Parent ActualWidth                Height   Binding RelativeSource  RelativeSource Self                Path Parent ActualHeight   gt           lt Canvas Name  Parent2  gt               lt Border Name  Parent3              Width   Binding RelativeSource  RelativeSource Self              Path Parent ActualWidth              Height   Binding RelativeSource  RelativeSource Self                 Path Parent ActualHeight   gt                  lt Canvas Name  Parent4  gt                  lt TextBlock FontSize  16                  Margin  5  Text  Display the name of the ancestor   gt                  lt TextBlock FontSize  16                    Margin  50               Text   Binding RelativeSource  RelativeSource                          FindAncestor                         AncestorType  x Type Border                           AncestorLevel 2  Path Name                           Width  200   gt                   lt  Canvas gt               lt  Border gt           lt  Canvas gt        lt  Border gt      lt  Canvas gt        The above situation is of two TextBlock elements those are embedded   within a series of borders and canvas elements those represent their   hierarchical parents  The second TextBlock will display the name of   the given parent at the relative source level       So try to change AncestorLevel 2 to AncestorLevel 1 and see what   happens  Then try to change the type of the ancestor from   AncestorType Border to AncestorType Canvas and see what s happens        The displayed text will change according to the Ancestor type and   level  Then what s happen if the ancestor level is not suitable to the   ancestor type  This is a good question  I know that you re about to   ask it  The response is no exceptions will be thrown and nothings will   be displayed at the TextBlock level           TemplatedParent         This mode enables tie a given ControlTemplate property to a property   of the control that the ControlTemplate is applied to  To well   understand the issue here is an example bellow   lt Window Resources gt   lt ControlTemplate x Key  template  gt           lt Canvas gt               lt Canvas RenderTransform gt                   lt RotateTransform Angle  20   gt                   lt  Canvas RenderTransform gt               lt Ellipse Height  100  Width  150                    Fill   Binding              RelativeSource  RelativeSource TemplatedParent               Path Background   gt                  lt  Ellipse gt               lt ContentPresenter Margin  35                     Content   Binding RelativeSource  RelativeSource                     TemplatedParent  Path Content    gt           lt  Canvas gt       lt  ControlTemplate gt   lt  Window Resources gt       lt Canvas Name  Parent0  gt       lt Button   Margin  50                 Template   StaticResource template   Height  0                 Canvas Left  0  Canvas Top  0  Width  0  gt           lt TextBlock FontSize  22  gt Click me lt  TextBlock gt       lt  Button gt    lt  Canvas gt        If I want to apply the properties of a given control to its control   template then I can use the TemplatedParent mode  There is also a   similar one to this markup extension which is the TemplateBinding   which is a kind of short hand of the first one  but the   TemplateBinding is evaluated at compile time at the contrast of the   TemplatedParent which is evaluated just after the first run time  As   you can remark in the bellow figure  the background and the content   are applied from within the button to the control template

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Some useful bits and pieces   Here s how to do it mostly in code   Binding b   new Binding    b RelativeSource   new RelativeSource RelativeSourceMode FindAncestor  this GetType    1   b Path   new PropertyPath  MyElementThatNeedsBinding    MyLabel SetBinding ContentProperty  b     I largely copied this from Binding Relative Source in code Behind   Also  the MSDN page is pretty good as far as examples go  RelativeSource Class

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I created a library to simplify the binding syntax of WPF including making it easier to use RelativeSource  Here are some examples  Before    Binding Path PathToProperty  RelativeSource  RelativeSource Self    Binding Path PathToProperty  RelativeSource  RelativeSource AncestorType  x Type typeOfAncestor     Binding Path PathToProperty  RelativeSource  RelativeSource TemplatedParent    Binding Path Text  ElementName MyTextBox    After    BindTo PathToProperty   BindTo Ancestor typeOfAncestor PathToProperty   BindTo Template PathToProperty   BindTo  MyTextBox Text    Here is an example of how method binding is simplified  Before      C  code private ICommand  saveCommand  public ICommand SaveCommand    get     if   saveCommand    null        saveCommand   new RelayCommand x   gt  this SaveObject           return  saveCommand        private void SaveObject         do something       XAML  Binding Path SaveCommand    After      C  code private void SaveObject         do something       XAML  BindTo SaveObject      You can find the library here  http   www simplygoodcode com 2012 08 simpler-wpf-binding html  Note in the  BEFORE  example that I use for method binding that code was already optimized by using RelayCommand which last I checked is not a native part of WPF  Without that the  BEFORE  example would have been even longer

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Don t forget TemplatedParent    lt Binding RelativeSource   RelativeSource TemplatedParent    gt    or   Binding RelativeSource  RelativeSource TemplatedParent

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Some useful bits and pieces   Here s how to do it mostly in code   Binding b   new Binding    b RelativeSource   new RelativeSource RelativeSourceMode FindAncestor  this GetType    1   b Path   new PropertyPath  MyElementThatNeedsBinding    MyLabel SetBinding ContentProperty  b     I largely copied this from Binding Relative Source in code Behind   Also  the MSDN page is pretty good as far as examples go  RelativeSource Class

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Here s a more visual explanation in the context of a MVVM architecture

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If you want to bind to another property on the object    Binding Path PathToProperty  RelativeSource  RelativeSource Self     If you want to get a property on an ancestor    Binding Path PathToProperty      RelativeSource  RelativeSource AncestorType  x Type typeOfAncestor      If you want to get a property on the templated parent  so you can do 2 way bindings in a ControlTemplate    Binding Path PathToProperty  RelativeSource  RelativeSource TemplatedParent     or  shorter  this only works for OneWay bindings     TemplateBinding Path PathToProperty

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If an element is not part of the visual tree  then RelativeSource will never work  In this case  you need to try a different technique  pioneered by Thomas Levesque  He has the solution on his blog under  WPF  How to bind to data when the DataContext is not inherited  And it works absolutely brilliantly  In the unlikely event that his blog is down  Appendix A contains a mirror copy of his article  Please do not comment here  please comment directly on his blog post  Appendix A  Mirror of blog post The DataContext property in WPF is extremely handy  because it is automatically inherited by all children of the element where you assign it  therefore you don   t need to set it again on each element you want to bind  However  in some cases the DataContext is not accessible  it happens for elements that are not part of the visual or logical tree  It can be very difficult then to bind a property on those elements    Let   s illustrate with a simple example  we want to display a list of products in a DataGrid  In the grid  we want to be able to show or hide the Price column  based on the value of a ShowPrice property exposed by the ViewModel  The obvious approach is to bind the Visibility of the column to the ShowPrice property   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding ShowPrice                  Converter  StaticResource visibilityConverter   quot   gt   Unfortunately  changing the value of ShowPrice has no effect  and the column is always visible    why  If we look at the Output window in Visual Studio  we notice the following line   System Windows Data Error  2   Cannot find governing FrameworkElement or FrameworkContentElement for target element  BindingExpression Path ShowPrice  DataItem null  target element is    DataGridTextColumn     HashCode 32685253   target property is    Visibility     type    Visibility     The message is rather cryptic  but the meaning is actually quite simple  WPF doesn   t know which FrameworkElement to use to get the DataContext  because the column doesn   t belong to the visual or logical tree of the DataGrid   We can try to tweak the binding to get the desired result  for instance by setting the RelativeSource to the DataGrid itself   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding DataContext ShowPrice                  Converter  StaticResource visibilityConverter                   RelativeSource  RelativeSource FindAncestor  AncestorType DataGrid   quot   gt   Or we can add a CheckBox bound to ShowPrice  and try to bind the column visibility to the IsChecked property by specifying the element name   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding IsChecked                  Converter  StaticResource visibilityConverter                   ElementName chkShowPrice  quot   gt   But none of these workarounds seems to work  we always get the same result    At this point  it seems that the only viable approach would be to change the column visibility in code-behind  which we usually prefer to avoid when using the MVVM pattern    But I   m not going to give up so soon  at least not while there are other options to consider  The solution to our problem is actually quite simple  and takes advantage of the Freezable class  The primary purpose of this class is to define objects that have a modifiable and a read-only state  but the interesting feature in our case is that Freezable objects can inherit the DataContext even when they   re not in the visual or logical tree  I don   t know the exact mechanism that enables this behavior  but we   re going to take advantage of it to make our binding work    The idea is to create a class  I called it BindingProxy for reasons that should become obvious very soon  that inherits Freezable and declares a Data dependency property  public class BindingProxy   Freezable        region Overrides of Freezable       protected override Freezable CreateInstanceCore                 return new BindingProxy                 endregion       public object Data               get   return  object GetValue DataProperty             set   SetValue DataProperty  value                    Using a DependencyProperty as the backing store for Data   This enables animation  styling  binding  etc        public static readonly DependencyProperty DataProperty           DependencyProperty Register  quot Data quot   typeof object   typeof BindingProxy   new UIPropertyMetadata null       We can then declare an instance of this class in the resources of the DataGrid  and bind the Data property to the current DataContext   lt DataGrid Resources gt       lt local BindingProxy x Key  quot proxy quot  Data  quot  Binding  quot    gt   lt  DataGrid Resources gt   The last step is to specify this BindingProxy object  easily accessible with StaticResource  as the Source for the binding   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding Data ShowPrice                  Converter  StaticResource visibilityConverter                   Source  StaticResource proxy   quot   gt   Note that the binding path has been prefixed with    Data     since the path is now relative to the BindingProxy object  The binding now works correctly  and the column is properly shown or hidden based on the ShowPrice property

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I created a library to simplify the binding syntax of WPF including making it easier to use RelativeSource  Here are some examples  Before    Binding Path PathToProperty  RelativeSource  RelativeSource Self    Binding Path PathToProperty  RelativeSource  RelativeSource AncestorType  x Type typeOfAncestor     Binding Path PathToProperty  RelativeSource  RelativeSource TemplatedParent    Binding Path Text  ElementName MyTextBox    After    BindTo PathToProperty   BindTo Ancestor typeOfAncestor PathToProperty   BindTo Template PathToProperty   BindTo  MyTextBox Text    Here is an example of how method binding is simplified  Before      C  code private ICommand  saveCommand  public ICommand SaveCommand    get     if   saveCommand    null        saveCommand   new RelayCommand x   gt  this SaveObject           return  saveCommand        private void SaveObject         do something       XAML  Binding Path SaveCommand    After      C  code private void SaveObject         do something       XAML  BindTo SaveObject      You can find the library here  http   www simplygoodcode com 2012 08 simpler-wpf-binding html  Note in the  BEFORE  example that I use for method binding that code was already optimized by using RelayCommand which last I checked is not a native part of WPF  Without that the  BEFORE  example would have been even longer

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Bechir Bejaoui exposes the use cases of the RelativeSources in WPF in his article here      The RelativeSource is a markup extension that is used in particular   binding cases when we try to bind a property of a given object to   another property of the object itself  when we try to bind a property   of a object to another one of its relative parents  when binding a   dependency property value to a piece of XAML in case of custom control   development and finally in case of using a differential of a series of   a bound data  All of those situations are expressed as relative source   modes  I will expose all of those cases one by one          Mode Self          Imagine this case  a rectangle that we want that its height is always   equal to its width  a square let s say  We can do this using the   element name   lt Rectangle Fill  Red  Name  rectangle                   Height  100  Stroke  Black                   Canvas Top  100  Canvas Left  100                  Width   Binding ElementName rectangle                  Path Height    gt        But in this above case we are obliged to indicate the name of the   binding object  namely the rectangle  We can reach the same purpose   differently using the RelativeSource    lt Rectangle Fill  Red  Height  100                  Stroke  Black                  Width   Binding RelativeSource  RelativeSource Self                  Path Height    gt        For that case we are not obliged to mention the name of the binding   object and the Width will be always equal to the Height whenever the   height is changed        If you want to parameter the Width to be the half of the height then   you can do this by adding a converter to the Binding markup extension    Let s imagine another case now     lt TextBlock Width   Binding RelativeSource  RelativeSource Self                  Path Parent ActualWidth    gt        The above case is used to tie a given property of a given element to   one of its direct parent ones as this element holds a property that is   called Parent  This leads us to another relative source mode which is   the FindAncestor one           Mode FindAncestor         In this case  a property of a given element will be tied to one of its   parents  Of Corse  The main difference with the above case is the fact   that  it s up to you to determine the ancestor type and the ancestor   rank in the hierarchy to tie the property  By the way try to play with   this piece of XAML   lt Canvas Name  Parent0  gt       lt Border Name  Parent1               Width   Binding RelativeSource  RelativeSource Self                Path Parent ActualWidth                Height   Binding RelativeSource  RelativeSource Self                Path Parent ActualHeight   gt           lt Canvas Name  Parent2  gt               lt Border Name  Parent3              Width   Binding RelativeSource  RelativeSource Self              Path Parent ActualWidth              Height   Binding RelativeSource  RelativeSource Self                 Path Parent ActualHeight   gt                  lt Canvas Name  Parent4  gt                  lt TextBlock FontSize  16                  Margin  5  Text  Display the name of the ancestor   gt                  lt TextBlock FontSize  16                    Margin  50               Text   Binding RelativeSource  RelativeSource                          FindAncestor                         AncestorType  x Type Border                           AncestorLevel 2  Path Name                           Width  200   gt                   lt  Canvas gt               lt  Border gt           lt  Canvas gt        lt  Border gt      lt  Canvas gt        The above situation is of two TextBlock elements those are embedded   within a series of borders and canvas elements those represent their   hierarchical parents  The second TextBlock will display the name of   the given parent at the relative source level       So try to change AncestorLevel 2 to AncestorLevel 1 and see what   happens  Then try to change the type of the ancestor from   AncestorType Border to AncestorType Canvas and see what s happens        The displayed text will change according to the Ancestor type and   level  Then what s happen if the ancestor level is not suitable to the   ancestor type  This is a good question  I know that you re about to   ask it  The response is no exceptions will be thrown and nothings will   be displayed at the TextBlock level           TemplatedParent         This mode enables tie a given ControlTemplate property to a property   of the control that the ControlTemplate is applied to  To well   understand the issue here is an example bellow   lt Window Resources gt   lt ControlTemplate x Key  template  gt           lt Canvas gt               lt Canvas RenderTransform gt                   lt RotateTransform Angle  20   gt                   lt  Canvas RenderTransform gt               lt Ellipse Height  100  Width  150                    Fill   Binding              RelativeSource  RelativeSource TemplatedParent               Path Background   gt                  lt  Ellipse gt               lt ContentPresenter Margin  35                     Content   Binding RelativeSource  RelativeSource                     TemplatedParent  Path Content    gt           lt  Canvas gt       lt  ControlTemplate gt   lt  Window Resources gt       lt Canvas Name  Parent0  gt       lt Button   Margin  50                 Template   StaticResource template   Height  0                 Canvas Left  0  Canvas Top  0  Width  0  gt           lt TextBlock FontSize  22  gt Click me lt  TextBlock gt       lt  Button gt    lt  Canvas gt        If I want to apply the properties of a given control to its control   template then I can use the TemplatedParent mode  There is also a   similar one to this markup extension which is the TemplateBinding   which is a kind of short hand of the first one  but the   TemplateBinding is evaluated at compile time at the contrast of the   TemplatedParent which is evaluated just after the first run time  As   you can remark in the bellow figure  the background and the content   are applied from within the button to the control template

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Here s a more visual explanation in the context of a MVVM architecture

User · Answer

If you want to bind to another property on the object    Binding Path PathToProperty  RelativeSource  RelativeSource Self     If you want to get a property on an ancestor    Binding Path PathToProperty      RelativeSource  RelativeSource AncestorType  x Type typeOfAncestor      If you want to get a property on the templated parent  so you can do 2 way bindings in a ControlTemplate    Binding Path PathToProperty  RelativeSource  RelativeSource TemplatedParent     or  shorter  this only works for OneWay bindings     TemplateBinding Path PathToProperty

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Some useful bits and pieces   Here s how to do it mostly in code   Binding b   new Binding    b RelativeSource   new RelativeSource RelativeSourceMode FindAncestor  this GetType    1   b Path   new PropertyPath  MyElementThatNeedsBinding    MyLabel SetBinding ContentProperty  b     I largely copied this from Binding Relative Source in code Behind   Also  the MSDN page is pretty good as far as examples go  RelativeSource Class

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If an element is not part of the visual tree  then RelativeSource will never work  In this case  you need to try a different technique  pioneered by Thomas Levesque  He has the solution on his blog under  WPF  How to bind to data when the DataContext is not inherited  And it works absolutely brilliantly  In the unlikely event that his blog is down  Appendix A contains a mirror copy of his article  Please do not comment here  please comment directly on his blog post  Appendix A  Mirror of blog post The DataContext property in WPF is extremely handy  because it is automatically inherited by all children of the element where you assign it  therefore you don   t need to set it again on each element you want to bind  However  in some cases the DataContext is not accessible  it happens for elements that are not part of the visual or logical tree  It can be very difficult then to bind a property on those elements    Let   s illustrate with a simple example  we want to display a list of products in a DataGrid  In the grid  we want to be able to show or hide the Price column  based on the value of a ShowPrice property exposed by the ViewModel  The obvious approach is to bind the Visibility of the column to the ShowPrice property   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding ShowPrice                  Converter  StaticResource visibilityConverter   quot   gt   Unfortunately  changing the value of ShowPrice has no effect  and the column is always visible    why  If we look at the Output window in Visual Studio  we notice the following line   System Windows Data Error  2   Cannot find governing FrameworkElement or FrameworkContentElement for target element  BindingExpression Path ShowPrice  DataItem null  target element is    DataGridTextColumn     HashCode 32685253   target property is    Visibility     type    Visibility     The message is rather cryptic  but the meaning is actually quite simple  WPF doesn   t know which FrameworkElement to use to get the DataContext  because the column doesn   t belong to the visual or logical tree of the DataGrid   We can try to tweak the binding to get the desired result  for instance by setting the RelativeSource to the DataGrid itself   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding DataContext ShowPrice                  Converter  StaticResource visibilityConverter                   RelativeSource  RelativeSource FindAncestor  AncestorType DataGrid   quot   gt   Or we can add a CheckBox bound to ShowPrice  and try to bind the column visibility to the IsChecked property by specifying the element name   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding IsChecked                  Converter  StaticResource visibilityConverter                   ElementName chkShowPrice  quot   gt   But none of these workarounds seems to work  we always get the same result    At this point  it seems that the only viable approach would be to change the column visibility in code-behind  which we usually prefer to avoid when using the MVVM pattern    But I   m not going to give up so soon  at least not while there are other options to consider  The solution to our problem is actually quite simple  and takes advantage of the Freezable class  The primary purpose of this class is to define objects that have a modifiable and a read-only state  but the interesting feature in our case is that Freezable objects can inherit the DataContext even when they   re not in the visual or logical tree  I don   t know the exact mechanism that enables this behavior  but we   re going to take advantage of it to make our binding work    The idea is to create a class  I called it BindingProxy for reasons that should become obvious very soon  that inherits Freezable and declares a Data dependency property  public class BindingProxy   Freezable        region Overrides of Freezable       protected override Freezable CreateInstanceCore                 return new BindingProxy                 endregion       public object Data               get   return  object GetValue DataProperty             set   SetValue DataProperty  value                    Using a DependencyProperty as the backing store for Data   This enables animation  styling  binding  etc        public static readonly DependencyProperty DataProperty           DependencyProperty Register  quot Data quot   typeof object   typeof BindingProxy   new UIPropertyMetadata null       We can then declare an instance of this class in the resources of the DataGrid  and bind the Data property to the current DataContext   lt DataGrid Resources gt       lt local BindingProxy x Key  quot proxy quot  Data  quot  Binding  quot    gt   lt  DataGrid Resources gt   The last step is to specify this BindingProxy object  easily accessible with StaticResource  as the Source for the binding   lt DataGridTextColumn Header  quot Price quot  Binding  quot  Binding Price  quot  IsReadOnly  quot False quot                  Visibility  quot  Binding Data ShowPrice                  Converter  StaticResource visibilityConverter                   Source  StaticResource proxy   quot   gt   Note that the binding path has been prefixed with    Data     since the path is now relative to the BindingProxy object  The binding now works correctly  and the column is properly shown or hidden based on the ShowPrice property

[.net] How do I use WPF bindings with RelativeSource?

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