Binding ItemsSource of a ComboBoxColumn in WPF DataGrid

Question

I have two simple Model classes and a ViewModel     public class GridItem       public string Name   get  set        public int CompanyID   get  set       public class CompanyItem       public int ID   get  set        public string Name   get  set       public class ViewModel       public ViewModel                 GridItems   new ObservableCollection lt GridItem gt                  new GridItem     Name    Jim   CompanyID   1               CompanyItems   new ObservableCollection lt CompanyItem gt                  new CompanyItem     ID   1  Name    Company 1                 new CompanyItem     ID   2  Name    Company 2                  public ObservableCollection lt GridItem gt  GridItems   get  set        public ObservableCollection lt CompanyItem gt  CompanyItems   get  set           and a simple Window    lt Window x Class  DataGridComboBoxColumnApp MainWindow          xmlns  http   schemas microsoft com winfx 2006 xaml presentation          xmlns x  http   schemas microsoft com winfx 2006 xaml          Title  MainWindow  Height  350  Width  525  gt       lt Grid gt           lt DataGrid AutoGenerateColumns  False  ItemsSource   Binding GridItems    gt               lt DataGrid Columns gt                   lt DataGridTextColumn Binding   Binding Name     gt                   lt DataGridComboBoxColumn ItemsSource   Binding CompanyItems                                       DisplayMemberPath  Name                                      SelectedValuePath  ID                                      SelectedValueBinding   Binding CompanyID     gt               lt  DataGrid Columns gt           lt  DataGrid gt       lt  Grid gt   lt  Window gt    The ViewModel is set to the MainWindow s DataContext in App xaml cs   public partial class App   Application       protected override void OnStartup StartupEventArgs e                base OnStartup e            MainWindow window   new MainWindow            ViewModel viewModel   new ViewModel             window DataContext   viewModel          window Show              As you can see I set the ItemsSource of the DataGrid to the GridItems collection of the ViewModel  This part works  the single Grid line with Name  Jim  is displayed   I also want to set the ItemsSource of the ComboBox in every row to the CompanyItems collection of the ViewModel  This part does not work  The ComboBox remains empty and in the Debugger Output Window I see an error message      System Windows Data Error  2   Cannot   find governing FrameworkElement or   FrameworkContentElement for target   element    BindingExpression Path CompanyItems    DataItem null  target element is    DataGridComboBoxColumn     HashCode 28633162   target property   is  ItemsSource   type  IEnumerable     I believe that WPF expects CompanyItems to be a property of GridItem which is not the case  and that s the reason why the binding fails   I ve already tried to work with a RelativeSource and AncestorType like so    lt DataGridComboBoxColumn ItemsSource   Binding CompanyItems       RelativeSource  RelativeSource Mode FindAncestor                                     AncestorType  x Type Window                             DisplayMemberPath  Name                          SelectedValuePath  ID                          SelectedValueBinding   Binding CompanyID     gt    But that gives me another error in the debugger output      System Windows Data Error  4   Cannot   find source for binding with reference    RelativeSource FindAncestor    AncestorType  System Windows Window     AncestorLevel  1      BindingExpression Path CompanyItems    DataItem null  target element is    DataGridComboBoxColumn     HashCode 1150788   target property is    ItemsSource   type  IEnumerable     Question  How can I bind the ItemsSource of the DataGridComboBoxColumn to the CompanyItems collection of the ViewModel  Is it possible at all   Thank you for help in advance

User · Answer

Your ComboBox is trying to bind to bind to GridItem[x].CompanyItems, which doesn't exist.

Your RelativeBinding is close, however it needs to bind to DataContext.CompanyItems because Window.CompanyItems does not exist

User · Answer

RookieRick is right  using DataGridTemplateColumn instead of DataGridComboBoxColumn gives a much simpler XAML    Moreover  putting the CompanyItem list directly accessible from the GridItem allows you to get rid of the RelativeSource    IMHO  this give you a very clean solution   XAML    lt DataGrid AutoGenerateColumns  False  ItemsSource   Binding GridItems    gt       lt DataGrid Resources gt           lt DataTemplate x Key  CompanyDisplayTemplate  DataType  vm GridItem  gt               lt TextBlock Text   Binding Company     gt           lt  DataTemplate gt           lt DataTemplate x Key  CompanyEditingTemplate  DataType  vm GridItem  gt               lt ComboBox SelectedItem   Binding Company   ItemsSource   Binding CompanyList     gt           lt  DataTemplate gt       lt  DataGrid Resources gt       lt DataGrid Columns gt           lt DataGridTextColumn Binding   Binding Name     gt           lt DataGridTemplateColumn CellTemplate   StaticResource CompanyDisplayTemplate                                   CellEditingTemplate   StaticResource CompanyEditingTemplate     gt       lt  DataGrid Columns gt   lt  DataGrid gt    View model   public class GridItem       public string Name   get  set        public CompanyItem Company   get  set        public IEnumerable lt CompanyItem gt  CompanyList   get  set       public class CompanyItem       public int ID   get  set        public string Name   get  set         public override string ToString     return Name       public class ViewModel       readonly ObservableCollection lt CompanyItem gt  companies       public ViewModel                 companies   new ObservableCollection lt CompanyItem gt               new CompanyItem   ID   1  Name    Company 1                 new CompanyItem   ID   2  Name    Company 2                        GridItems   new ObservableCollection lt GridItem gt                new GridItem   Name    Jim   Company   companies 0   CompanyList   companies                        public ObservableCollection lt GridItem gt  GridItems   get  set

User · Answer

the bast way i use i bind the textblock and combobox to same property and this property should support notifyPropertyChanged   i used relativeresource to bind to parent view datacontext which is usercontrol to go up datagrid level in binding because in this case the datagrid will search in object that you used in datagrid itemsource        lt DataGridTemplateColumn Header  your columnName  gt        lt DataGridTemplateColumn CellTemplate gt             lt DataTemplate gt                lt TextBlock Text   Binding RelativeSource  RelativeSource AncestorType  x Type UserControl    Path DataContext SelectedUnit Name  Mode TwoWay     gt              lt  DataTemplate gt        lt  DataGridTemplateColumn CellTemplate gt        lt DataGridTemplateColumn CellEditingTemplate gt              lt DataTemplate gt               lt ComboBox DisplayMemberPath  Name                        IsEditable  True                        ItemsSource   Binding RelativeSource  RelativeSource AncestorType  x Type UserControl    Path DataContext UnitLookupCollection                          SelectedItem   Binding RelativeSource  RelativeSource AncestorType  x Type UserControl    Path DataContext SelectedUnit  Mode TwoWay  UpdateSourceTrigger PropertyChanged                         SelectedValue   Binding UnitId  Mode TwoWay  UpdateSourceTrigger PropertyChanged                         SelectedValuePath  Id    gt               lt  DataTemplate gt       lt  DataGridTemplateColumn CellEditingTemplate gt   lt  DataGridTemplateColumn gt

User · Answer

The documentation on MSDN about the ItemsSource of the DataGridComboBoxColumn says that only static resources  static code or inline collections of combobox items can be bound to the ItemsSource      To populate the drop-down list  first   set the ItemsSource property for the   ComboBox by using one of the following   options          A static resource  For more information  see StaticResource Markup   Extension    An x Static code entity  For more information  see x Static Markup   Extension    An inline collection of ComboBoxItem types       Binding to a DataContext s property is not possible if I understand that correctly   And indeed  When I make CompanyItems a static property in ViewModel      public static ObservableCollection lt CompanyItem gt  CompanyItems   get  set          add the namespace where the ViewModel is located to the window      xmlns vm  clr-namespace DataGridComboBoxColumnApp        and change the binding to       lt DataGridComboBoxColumn     ItemsSource   Binding Source  x Static vm ViewModel CompanyItems         DisplayMemberPath  Name      SelectedValuePath  ID      SelectedValueBinding   Binding CompanyID     gt        then it works  But having the ItemsSource as a static property might be sometimes OK  but it is not always what I want

User · Answer

The correct solution seems to be    lt Window Resources gt       lt CollectionViewSource x Key  ItemsCVS  Source   Binding MyItems     gt   lt  Window Resources gt   lt  --     -- gt   lt DataGrid ItemsSource   Binding MyRecords   gt       lt DataGridComboBoxColumn Header  Column With Predefined Values                              ItemsSource   Binding Source  StaticResource ItemsCVS                                SelectedValueBinding   Binding MyItemId                               SelectedValuePath  Id                              DisplayMemberPath  StatusCode    gt   lt  DataGrid gt    The layout above works perfectly fine for me  and should work for others  This design choice also makes sense  though it isn t very well explained anywhere  But if you have a data column with predefined values  those values typically don t change during run-time  So creating a CollectionViewSource and initializing the data once makes sense  It also gets rid of the longer bindings to find an ancestor and bind on it s data context  which always felt wrong to me    I am leaving this here for anyone else who struggled with this binding  and wondered if there was a better way  As this page is obviously still coming up in search results  that s how I got here

User · Answer

Pls  check if DataGridComboBoxColumn xaml below would work for you    lt DataGridComboBoxColumn      SelectedValueBinding   Binding CompanyID        DisplayMemberPath  Name       SelectedValuePath  ID  gt        lt DataGridComboBoxColumn ElementStyle gt           lt Style TargetType   x Type ComboBox   gt               lt Setter Property  ItemsSource  Value   Binding Path DataContext CompanyItems  RelativeSource  RelativeSource AncestorType  x Type Window       gt           lt  Style gt       lt  DataGridComboBoxColumn ElementStyle gt       lt DataGridComboBoxColumn EditingElementStyle gt           lt Style TargetType   x Type ComboBox   gt               lt Setter Property  ItemsSource  Value   Binding Path DataContext CompanyItems  RelativeSource  RelativeSource AncestorType  x Type Window       gt           lt  Style gt       lt  DataGridComboBoxColumn EditingElementStyle gt   lt  DataGridComboBoxColumn gt    Here you can find another solution for the problem you re facing  Using combo boxes with the WPF DataGrid

User · Answer

I realize this question is over a year old  but I just stumbled across it in dealing with a similar problem and thought I would share another potential solution in case it might help a future traveler  or myself  when I forget this later and find myself flopping around on StackOverflow between screams and throwings of the nearest object on my desk    In my case I was able to get the effect I wanted by using a DataGridTemplateColumn instead of a DataGridComboBoxColumn  a la the following snippet    caveat  I m using  NET 4 0  and what I ve been reading leads me to believe the DataGrid has done a lot of evolving  so YMMV if using earlier version    lt DataGridTemplateColumn Header  Identifier TEMPLATED  gt       lt DataGridTemplateColumn CellEditingTemplate gt           lt DataTemplate gt               lt ComboBox IsEditable  False                   Text   Binding ComponentIdentifier Mode TwoWay UpdateSourceTrigger PropertyChanged                   ItemsSource   Binding Path ApplicableIdentifiers  Mode OneWay  UpdateSourceTrigger PropertyChanged     gt           lt  DataTemplate gt       lt  DataGridTemplateColumn CellEditingTemplate gt       lt DataGridTemplateColumn CellTemplate gt           lt DataTemplate gt               lt TextBlock Text   Binding ComponentIdentifier     gt           lt  DataTemplate gt       lt  DataGridTemplateColumn CellTemplate gt   lt  DataGridTemplateColumn gt

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