Datagrid problem..

Hi,
I have a datagrid with certain template columns ,
 <my:DataGrid x:Name="dg1" Canvas.Top="160" Canvas.Left="150"  Height="200" Width="600" AutoGenerateColumns="False"
                     HeadersVisibility="Column" GridlinesVisibility="None" >
            <my:DataGrid.Columns>
                        <my:DataGridTemplateColumn Header="From">
                            <my:DataGridTemplateColumn.CellTemplate>
  & ...