WPF: Binding an Element in a DataGridTemplateColumn to an Element in another DataGridTemplateColumn

Question

:) I have one DataGrid. In Column2 there is "ComboBox1", in Column3 there is "ComboBox2". I would like to set IsEnabled to false on "ComboBox2" as long as "ComboBox1" has SelectedIndex=0. For each row seperately.

This works perfectly outside the Datagrid with two ComboBoxes (with the help of Style and DataTrigger). However, inside the Datagrid, within Column3 I cannot "see" "ComboBox1" ("Cannot find source for binding...").

It's basically a namescope issue. However, referring to a Combobox within a DataGrid by name seems to be wrong in the first place. So: any ideas how to accomplish this?

Thank you very much in advance!

<Window.Resources>
    <CollectionViewSource x:Key="Source1" Source="{Binding List1}" />
    <CollectionViewSource x:Key="Source2" Source="{Binding List2}" />
</Window.Resources>

<DataGrid x:Name="ModelControl" AutoGenerateColumns="False" ItemsSource="{Binding List3}">
    <DataGrid.Columns>
         <DataGridTextColumn Binding="{Binding MyName}" Header="Modellname" />
        <DataGridTemplateColumn Header="Header 1">
            <DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <ComboBox x:Name="ComboBox1" DisplayMemberPath="MyName" SelectedIndex="0">
                        <ComboBox.ItemsSource>
                            <CompositeCollection>
                                <CollectionContainer Collection="{Binding Source={StaticResource Source2}}" />
                            </CompositeCollection>
                        </ComboBox.ItemsSource>
                    </ComboBox>
                </DataTemplate>
            </DataGridTemplateColumn.CellTemplate>
        </DataGridTemplateColumn>
        <DataGridTemplateColumn Header="Header 2">
            <DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <ComboBox x:Name="ComboBox2" DisplayMemberPath="MyName">
                        <ComboBox.Style>
                            <Style TargetType="{x:Type ComboBox}">
                                <Setter Property="IsEnabled" Value="True" />
                                <Style.Triggers>
                                    <DataTrigger Binding="{Binding SelectedIndex,ElementName=ComboBox1}" Value="0">
                                        <Setter Property="IsEnabled" Value="False" />
                                    </DataTrigger>
                                </Style.Triggers>
                            </Style>
                        </ComboBox.Style>
                        <ComboBox.ItemsSource>
                            <CompositeCollection>
                                <CollectionContainer Collection="{Binding Source={StaticResource Source1}}" />
                            </CompositeCollection>
                        </ComboBox.ItemsSource>
                    </ComboBox>
                </DataTemplate>
            </DataGridTemplateColumn.CellTemplate>
        </DataGridTemplateColumn>
    </DataGrid.Columns>
</DataGrid>

Please don't mind the CompositeCollection.

Answer 1

However, referring to a Combobox within a DataGrid by name seems to be wrong in the first place. So: any ideas how to accomplish this?

You should bind the SelectedIndex property to a source property of your model class:

<DataGrid x:Name="ModelControl" AutoGenerateColumns="False" ItemsSource="{Binding List3}">
    <DataGrid.Columns>
        <DataGridTextColumn Binding="{Binding MyName}" Header="Modellname" />
        <DataGridTemplateColumn Header="Header 1">
            <DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <ComboBox x:Name="ComboBox1" DisplayMemberPath="MyName" 
                                      SelectedIndex="{Binding YourIndexProperty}">
                        <ComboBox.ItemsSource>
                            <CompositeCollection>
                                <CollectionContainer Collection="{Binding Source={StaticResource Source2}}" />
                            </CompositeCollection>
                        </ComboBox.ItemsSource>
                    </ComboBox>
                </DataTemplate>
            </DataGridTemplateColumn.CellTemplate>
        </DataGridTemplateColumn>
        <DataGridTemplateColumn Header="Header 2">
            <DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <ComboBox x:Name="ComboBox2" DisplayMemberPath="MyName">
                        <ComboBox.Style>
                            <Style TargetType="{x:Type ComboBox}">
                                <Setter Property="IsEnabled" Value="True" />
                                <Style.Triggers>
                                    <DataTrigger Binding="{Binding YourIndexProperty}" Value="0">
                                        <Setter Property="IsEnabled" Value="False" />
                                    </DataTrigger>
                                </Style.Triggers>
                            </Style>
                        </ComboBox.Style>
                        <ComboBox.ItemsSource>
                            <CompositeCollection>
                                <CollectionContainer Collection="{Binding Source={StaticResource Source1}}" />
                            </CompositeCollection>
                        </ComboBox.ItemsSource>
                    </ComboBox>
                </DataTemplate>
            </DataGridTemplateColumn.CellTemplate>
        </DataGridTemplateColumn>
    </DataGrid.Columns>
</DataGrid>

Make sure that the model type implements the INotifyPropertyChanged interface and raise the PropertyChanged event in the setter: https://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged(v=vs.110).aspx

Answer 2

try something like this:

Modify your combobox1 by adding the selected id SelectedValue="{Binding List3ComboBox1ItemId}", the List3ComboBox1ItemId property must be a property of list3

<ComboBox x:Name="ComboBox1" DisplayMemberPath="MyName" SelectedValue="{Binding List3ComboBox1ItemId}">
    <ComboBox.ItemsSource>
        <CompositeCollection>
            <CollectionContainer Collection="{Binding Source={StaticResource Source2}}" />
        </CompositeCollection>
    </ComboBox.ItemsSource>
</ComboBox>

and your combobox2 you have to include a converter to verify your id, if id > 0 returns true. (not included in this answer)

<ComboBox x:Name="ComboBox2" DisplayMemberPath="MyName" SelectedItem="{Binding List3ComboBox2Item}"  IsEnabled={Binding List3ComboBox1ItemId, Converter={StaticResource IntegerToBoolConverter}} >