RadComboBox within DataGrid

[Geoff Ables]

When I put the RadCombo in a DataGridTemplateColumn, it displays only the first item and selecting the expand error does not expand the list.  The xaml below results in the 'Ascending' Combobox being displayed in each row, but does not allow changing the selection or even showing that there is other selections

<

my:DataGrid x:Name="gridColumns" AutoGenerateColumns="False" >

<my:DataGrid.Columns>

<my:DataGridTextColumn Header="Column Name" DisplayMemberBinding="{Binding ColumnName}"/>

<my:DataGridTextColumn Header="Alias" DisplayMemberBinding="{Binding Alias}"/>

<my:DataGridTextColumn Header="Table" DisplayMemberBinding="{Binding Table}"/>

<my:DataGridCheckBoxColumn Header="Output" DisplayMemberBinding="{Binding Output}"/>

<my:DataGridTemplateColumn Header="Sort Type">

<my:DataGridTemplateColumn.CellTemplate>

<DataTemplate>

<Grid >

<telerik:RadComboBox SelectedItem="{Binding SortType}" >

<telerik:RadComboBoxItem Content="Ascending" />

<telerik:RadComboBoxItem Content="Descending" />

</telerik:RadComboBox>

</Grid>

</DataTemplate>

</my:DataGridTemplateColumn.CellTemplate>

</my:DataGridTemplateColumn>

</my:DataGrid.Columns>

</my:DataGrid>

[Valeri Hristov]

Hi Geoff,

I managed to reproduce the problem. It appears that the combo box dropdown is not measured correctly when the combo is placed in CellTemplate, but works properly when it is placed in CellEditingTemplate. We are planning an update of RadControls for Silverlight in several days and I will try to include the fix if this problem in it.

Unfortunately, at this moment I am unable to offer a quick workaround, different than using RadComboBox in CellEditingTemplate, instead of CellTemplate.

I am sorry for the inconvenience.

All the best,
Valeri Hristov
the Telerik team

Check out Telerik Trainer, the state of the art learning tool for Telerik products.

[Simon Kingaby]

This is currently a bug in the Silverlight DataGrid control.  When a ComboBox or RadComboBox is included in a DataGridTemplateColumn.CellEditingTemplate,  the ComboBox dropdown autohides immediately after clicking the dropdown button. 

Manish Dalal's blog has the fix for this:  http://weblogs.asp.net/manishdalal/archive/2008/09/28/combobox-in-datagrid.aspx 

You first create a utility class that will provide the "keep drop list open" service to the combo box, like this:

Imports Telerik.Windows.Controls

Public Class RadComboBoxService

    Public Shared ReadOnly ForceOpenProperty As DependencyProperty = _
        DependencyProperty.RegisterAttached("ForceOpen", GetType(Boolean), GetType(RadComboBoxService), New PropertyMetadata(AddressOf OnForceOpenChanged))

    Public Shared Function GetForceOpen(ByVal d As DependencyObject) As Boolean
        Return d.GetValue(ForceOpenProperty)
    End Function

    Public Shared Sub SetForceOpen(ByVal d As DependencyObject, ByVal value As Boolean)
        d.SetValue(ForceOpenProperty, value)
    End Sub

    Private Shared Sub OnForceOpenChanged(ByVal d As DependencyObject, ByVal e As DependencyPropertyChangedEventArgs)
        Dim comboBox = DirectCast(d, RadComboBox)
        If CBool(e.OldValue) Then
            RemoveHandler comboBox.Loaded, New RoutedEventHandler(AddressOf comboBox_Loaded)
        End If
        If CBool(e.NewValue) Then
            AddHandler comboBox.Loaded, New RoutedEventHandler(AddressOf comboBox_Loaded)
        End If
    End Sub

    Shared Sub comboBox_Loaded(ByVal sender As Object, ByVal e As RoutedEventArgs)
        Dim comboBox = DirectCast(sender, RadComboBox)
        If comboBox Is Nothing Then
            comboBox = DirectCast(e.OriginalSource, RadComboBox)
        End If
        comboBox.IsDropDownOpen = True
    End Sub

End Class

You then use the service in the XAML declaration of your RadComboBox like this:

<data:DataGridTemplateColumn.CellEditingTemplate>
    <DataTemplate>
        <telerik:RadComboBox x:Name="DealTypeIdCombo" Margin="1,0,1,0"
Width="200" DisplayMemberPath="Descr" VerticalAlignment="Center"
Height="25" SelectedItem="{Binding DealTypeId, Mode=TwoWay}"
ItemsSource="{Binding SourceDealTypes, Source={StaticResource localItemSource}}"
local:RadComboBoxService.ForceOpen="true">
        </telerik:RadComboBox>
    </DataTemplate>
</data:DataGridTemplateColumn.CellEditingTemplate>

Notice the attribute local:RadComboBoxService.ForceOpen="true"