Problem binding DataGridComboBoxColumn.ItemsSource

Question

I have 3 tables: Item - which is the DataContext - it has a navigation column Group Group - has a navigation column Category.

I want to have in the DataGrid both (Category & Group) columns and when I choose a category it should display in the group col only the Category.Groups.

Here is the code I am working on:

<tk:DataGrid AutoGenerateColumns="False" ItemsSource="{Binding}">
    <tk:DataGrid.Columns>

        <!--Works-->
        <tk:DataGridComboBoxColumn                                        
            Header="Categroy" 
            DisplayMemberPath="Title"                    
            SelectedValuePath="CategoryId"
            SelectedValueBinding="{Binding Group.Category.CategoryId}"
            ItemsSource="{Binding Context.Categories, 
                Source={x:Static Application.Current}}"
        />


        <!--Look at these two things:-->

        <!--This does work-->
        <tk:DataGridTemplateColumn>
            <tk:DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <ItemsControl
                        ItemsSource="{Binding Group.Category.Groups}">
                        <ItemsControl.ItemTemplate>
                            <DataTemplate DataType="{x:Type data:Group}">
                                <TextBlock Text="{Binding Title}"/>
                            </DataTemplate>
                        </ItemsControl.ItemTemplate>
                    </ItemsControl>
                </DataTemplate>
            </tk:DataGridTemplateColumn.CellTemplate>
        </tk:DataGridTemplateColumn>

        <!--But this does NOT work, even it's the same source-->
        <!--Notice I even tried a dummy converter and doesnt reach there-->
        <tk:DataGridComboBoxColumn 
            Header="Group" 
            DisplayMemberPath="Title"
            SelectedValuePath="GroupId"
            ItemsSource="{Binding Group.Category.Groups,
                Converter={StaticResource DummyConverter}}"
            SelectedValueBinding="{Binding Group.GroupId}"
            />

    </tk:DataGrid.Columns>
</tk:DataGrid>

Update
Would you say the problem is that the ItemsSource property cannot be set to a non-static Binding? I suspect so because even I set the ItemsSource to {Binding} with the DummyConverter it doesn't stop in the converter; and in the Category ComboBox it works fine.

Community · Accepted Answer · 2017-05-23 11:46:36Z

34

The columns in the datagrid don't have a datacontext, as they are never added to the visual tree. sound a bit weird but have a look at vince's blog, its got a good example of the visual layout. once the grid is drawn the cells have a data context and you can set the combo boxes items source in them using normal bindings (not static resources..)

You can access the combo box items source as such:

<dg:DataGridComboBoxColumn>
   <dg:DataGridComboBoxColumn.EditingElementStyle>
      <Style TargetType="ComboBox">
         <Setter Property="ItemsSource" Value="{Binding Path=MyBindingPath}" />
      </Style>
   </dg:DataGridComboBoxColumn.EditingElementStyle>
</dg:DataGridComboBoxColumn>

Have a look here and also here for some code. You will also need to set the items source for the non edting element as in this post

edited May 23, 2017 at 11:46

CommunityBot

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answered Nov 15, 2009 at 11:42

Aran Mulholland

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6 Comments

newman Over a year ago

How to make it work for .NET 4.0 Datagrid? Vince's blog seems to be out-dated.

Aran Mulholland Over a year ago

I don't think the datagrid's implementation of the ComboColumn changed in the .net 4 release

Nps Over a year ago

I used same approach, but datasource doesn't seems to bind the column. I am seeing empty combobox in DataGrid

Aran Mulholland Over a year ago

Chuck a debugConverter on it and see if the bindings ever fire (wpftutorial.net/DebugDataBinding.html)

William Over a year ago

Shouldn't it also work just to target a particular ElementName that has a DataContext?

|

John Henckel · Accepted Answer · 2017-08-29 19:01:31Z

9

I was using MVVM and I wanted to bind the ItemSource of the column to a collection of objects in the window data context. I must have tried 10 different ways and nothing worked until I found this answer.

The trick is to define a CollectionViewSource outside the grid and then reference it inside the grid using StaticResource. For example,

<Window.Resources>
    <CollectionViewSource x:Key="ItemsCVS" Source="{Binding MyItems}" />
</Window.Resources>
<!-- ... -->
<DataGrid ItemsSource="{Binding MyRecords}">
    <DataGridComboBoxColumn Header="Column With Predefined Values"
                            ItemsSource="{Binding Source={StaticResource ItemsCVS}}"
                            SelectedValueBinding="{Binding MyItemId}"
                            SelectedValuePath="Id"
                            DisplayMemberPath="StatusCode" />
</DataGrid>

answered Aug 29, 2017 at 19:01

John Henckel

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1 Comment

vladimir khozeyev Over a year ago

I think this decision is simpler than using proxy elements... Thanks!

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