ComboBox in DataForm, SL4 - silverlight-4.0

Question

I know that this question is what many of you already posted, but I'm still having a problem. The idea is very simple: I have a DataGrid and when I select the item in DataGrid, it should select item in ComboBox which is in DataForm. I have read many posts, and implemented few ideas in what I did, and now, I have this:
<StackPanel Grid.Column="1" Grid.Row="4" Name="stackPanel1" Margin="0,0,0,-257">
<sdk:DataGrid Name="PhysicalQuantitiesGrid"
MinHeight="100" IsReadOnly="True"
Margin="0,12,0,0"
ItemsSource="{Binding PhysicalQuantities}"
SelectedItem="{Binding Path=CurrentPhysicalQuantity, Mode=TwoWay}"
AutoGenerateColumns="False" VerticalGridLinesBrush="{x:Null}">
<sdk:DataGrid.RowDetailsTemplate>
<DataTemplate>
<StackPanel Orientation="Vertical" Margin="5">
<StackPanel Orientation="Horizontal" Margin="5">
<StackPanel Orientation="Vertical" Margin="5">
<TextBlock
FontSize="12"
Width="Auto"
Text="Base unit term"/>
<TextBlock
Foreground="CadetBlue"
FontSize="12"
Width="Auto"
TextWrapping="Wrap"
Text="{Binding Path=Unit.Term}"/>
</StackPanel>
<StackPanel Orientation="Vertical" Margin="5">
<TextBlock
FontSize="12"
Width="Auto"
Text="Short term"/>
<TextBlock
Foreground="CadetBlue"
FontSize="12"
Width="Auto"
TextWrapping="Wrap"
Text="{Binding Path=Unit.ShortTerm}"/>
</StackPanel>
</StackPanel>
</StackPanel>
</DataTemplate>
</sdk:DataGrid.RowDetailsTemplate>
<sdk:DataGrid.Columns>
<sdk:DataGridTextColumn Header="Term"
Binding="{Binding Path=Term}"
FontSize="14"
Foreground="DarkBlue"
>
</sdk:DataGridTextColumn>
</sdk:DataGrid.Columns>
</sdk:DataGrid>
<StackPanel Orientation="Horizontal" HorizontalAlignment="Right" Margin="0,12,0,0">
<Button x:Name="NewPhysicalQuantity" Content="AddNew" Height="23" Click="NewPhysicalQuantity_Click"/>
</StackPanel>
<dataform:DataForm x:Name="PhysicalQuantityDetails"
Header="Fizicke velicine - detalji"
AutoGenerateFields="False"
AutoEdit="False"
CommandButtonsVisibility="Commit,Cancel,Edit"
Margin="0,12,0,0"
CurrentItem="{Binding Path=CurrentPhysicalQuantity}"
CancelButtonContent="Cancel"
CommitButtonContent="Commit"
>
<dataform:DataForm.EditTemplate>
<DataTemplate>
<StackPanel>
<dataform:DataField Label="Physical Quantity term:">
<TextBox Text="{Binding Path=Term, Mode=TwoWay}" />
</dataform:DataField>
<dataform:DataField Label="Base unit">
<StackPanel>
<riaControls:DomainDataSource AutoLoad="True" Height="0" Name="baseUnitsDataSource" QueryName="GetBaseUnitsOrdered" Width="0">
<riaControls:DomainDataSource.DomainContext>
<myService:DomainDomainContext/>
</riaControls:DomainDataSource.DomainContext>
</riaControls:DomainDataSource>
<myControl:ComboBox
ItemsSource="{Binding ElementName=baseUnitsDataSource, Path=Data}"
SelectedValuePath="IDUnit"
DisplayMemberPath="Term"
SelectedValue="{Binding Path=IDUnit, Mode=TwoWay}"
>
<ComboBox.ItemsPanel>
<ItemsPanelTemplate>
<VirtualizingStackPanel />
</ItemsPanelTemplate>
</ComboBox.ItemsPanel>
</myControl:ComboBox>
</StackPanel>
</dataform:DataField>
</StackPanel>
</DataTemplate>
</dataform:DataForm.EditTemplate>
</dataform:DataForm>
<StackPanel
Orientation="Horizontal"
HorizontalAlignment="Right"
Margin="0,12,0,0">
<Button
Content="Save"
x:Name="SaveChangesButton"
Width="100"
Height="23"
Margin="4,0,4,0"
Command="{Binding SaveCommand}" />
</StackPanel>
</StackPanel>
So, I use MVVM with RIA. For data grid I use MVVM, and for ComboBox data context I use RIA. That is the only way to fill the ComboBox and to bind DataGrid value with ComboBox value, but in the wrong way! When I click Edit in data form, I always get ComboBox initialized to the first item. Of course, value in data grid get the same value (wrong!).
What I am doing wrong?
Thanks!
P.S. I forgot to mention that I have two tables, PhysicalQuantity and Unit, where PhysicalQuantity has one or zero Units (BaseUnit).
Lucky

Answer 1

You're using the wrong ComboBox.
Kyle McClellan has a far more capable ComboBox, which honestly should have been rolled out with the toolkit 2 times over by now, but there seems to be something going fishy with toolkit support as well. Please read more about it here:
http://blogs.msdn.com/b/kylemc/archive/2010/06/18/combobox-sample-for-ria-services.aspx