WPF Binding to parent DataContext

Question

We have a WPF application with a standard MVVM pattern  leveraging Cinch  and therefore MefedMVVM  for View -  ViewModel resolution  This works well  and I can bind the relevant controls to properties on the ViewModel   Within a particular View  we have an Infragistics XamGrid  This grid is bound to an ObservableCollection on the ViewModel  and displays the appropriate rows  However  I then have a specific column on this grid which I am trying to bind a TextBox text value to a property on the parent DataContext  rather than the ObservableCollection  This binding is failing   We ve gone through several options here including    Using AncestorType to track up the tree and bind to the DataContext of the parent UserControl like so  from the great answer to this question  as well as this one       Binding Path PathToProperty  RelativeSource  RelativeSource AncestorType  x Type typeOfAncestor     Specifying the ElementName and trying to target the top level control directly  Have a look here if you d like to read about using ElementName  Using a  proxy  FrameorkElement defined in the resources for the UserControl to try and  pass in  the context as required  We define the element as below  then reference as a static resource      lt FrameworkElement x Key  ProxyContext  DataContext   Binding Path DataContext  RelativeSource  RelativeSource Self    gt  lt  FrameworkElement gt     In this case the binding finds the FrameworkElement  but can not access anything beyond that  when specifying a Path    Having read around  it looks quite likely that this is caused by the Infragistics XamGrid building columns outside of the tree  However  even if this is the case  at least options 2 or 3 should work   Our last thoughts are that it is related to the V - VM binding  but even using Snoop we ve yet to find what the exact issue is  I m by no means an expert with WPF binding so any pointers would be appreciated   EDIT  I have found some templating examples from Infragistics here that I will try   EDIT 2  As pointed out by  Dtex  templates are the way to go  Here is the relevant snippet for use with a XamGrid    lt ig GroupColumn Key  CurrentDate  gt                   lt ig GroupColumn HeaderTemplate gt                       lt DataTemplate gt                           lt TextBlock Text   Binding Path DataContext CurrentDateTest  RelativeSource  RelativeSource AncestorType UserControl      gt                       lt  DataTemplate gt                   lt  ig GroupColumn HeaderTemplate gt                   lt ig GroupColumn Columns gt    I ve left the XML open    you d simply add the columns you wanted  then close off the relevant tags

User · Accepted Answer

I dont know about XamGrid but that s what i ll do with a standard wpf DataGrid    lt DataGrid gt       lt DataGrid Columns gt           lt DataGridTemplateColumn gt               lt DataGridTemplateColumn CellTemplate gt                   lt DataTemplate gt                       lt TextBlock Text   Binding DataContext MyProperty  RelativeSource  RelativeSource AncestorType MyUserControl     gt                   lt  DataTemplate gt               lt  DataGridTemplateColumn CellTemplate gt               lt DataGridTemplateColumn CellEditingTemplate gt                   lt DataTemplate gt                       lt TextBox Text   Binding DataContext MyProperty  RelativeSource  RelativeSource AncestorType MyUserControl     gt                   lt  DataTemplate gt               lt  DataGridTemplateColumn CellEditingTemplate gt           lt  DataGridTemplateColumn gt       lt  DataGrid Columns gt   lt  DataGrid gt    Since the TextBlock and the TextBox specified in the cell templates will be part of the visual tree  you can walk up and find whatever control you need

User · Answer

Because of things like this  as a general rule of thumb  I try to avoid as much XAML  trickery  as possible and keep the XAML as dumb and simple as possible and do the rest in the ViewModel  or attached properties or IValueConverters etc  if really necessary    If possible I would give the ViewModel of the current DataContext a reference  i e  property  to the relevant parent ViewModel  public class ThisViewModel   ViewModelBase       TypeOfAncestorViewModel Parent   get  set        and bind against that directly instead    lt TextBox Text   Binding Parent     gt

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