Custom controls and data binding problem

[Raman]

Hi
I have a Radgrid that one column is a button. I make it in xaml. but when i bind a query to datagrid like: radGridTest.ItemsSource = query; data does not appear but when i bind it to a simple radgrid (which has no button column) every thing goes fine. the way i make the button column is here:
...
                   <telerik:GridViewDataColumn.CellTemplate>
                        <DataTemplate >
                            <StackPanel Orientation="Horizontal">
                                <Button Width="25" Height="25" Background="Red"/>
                            </StackPanel>
                        </DataTemplate>
                    </telerik:GridViewDataColumn.CellTemplate>
...