I have a WPF 4 app with a ComboBox embedded in a DataGrid. The ComboBox is in a template column that displays the combobox when in edit mode but just a TextBlock otherwise. If I edit the cell and pick a new value from the combobox, when leaving the cell, the TextBlock in view mode does not reflect the new value. Ultimately, the new value gets saved and is displayed when the window is refreshed but it does not happen while still editing in the grid.

Here are the parts that are making this more complicated. The grid and the combobox are bound to different ItemsSource from the EnityFramework which is tied to my database. For this problem, the grid is displaying project members. The project member name can be picked from the combobox which gives a list of all company employees.

Any ideas on how to tie the view mode of the DataGridColumnTemplate to the edit value when they are pointing to different DataSources?

Relevant XAML

<Window.Resources>
    <ObjectDataProvider x:Key="EmployeeODP" />
</Window.Resources>
<StackPanel>
<DataGrid Name="teamProjectGrid"  AutoGenerateColumns="false" ItemsSource="{Binding  Path=ProjectMembers}"
       <DataGrid.Columns>
          <DataGridTemplateColumn Header="Name" x:Name="colProjectMember">
             <DataGridTemplateColumn.CellTemplate>
            <DataTemplate>
               <TextBlock Text="{Binding Path=ProjectMemberFullName}" />
            </DataTemplate>
          </DataGridTemplateColumn.CellTemplate>
          <DataGridTemplateColumn.CellEditingTemplate>
            <DataTemplate>
               <ComboBox x:Name="ProjectMemberCombo" IsReadOnly="True"
                  DisplayMemberPath="FullName"
                  SelectedValue="{Binding Path=Employee}"
                  ItemsSource="{Binding Source={StaticResource EmployeeODP}}"
                />
            </DataTemplate>
         </DataGridTemplateColumn.CellEditingTemplate>
      </DataGridTemplateColumn>
      <DataGridTextColumn x:Name="colProjectRole" Binding="{Binding Path=ProjectRole}" Header="Role" />
   </DataGrid.Columns>
</DataGrid>
</StackPanel>

Relevant Code Behind

this.DataContext = new MyEntityLibrary.MyProjectEntities();

ObjectDataProvider EmployeeODP= (ObjectDataProvider)FindResource("EmployeeODP");
if (EmployeeODP != null)
{
   EmployeeODP.ObjectInstance = this.DataContext.Employees;
}