<sdk:DataGrid.Columns>
 <sdk:DataGridTemplateColumn Width="30" IsReadOnly="True" CanUserReorder="False" CanUserResize="False" CanUserSort="False" Header="*">
 <sdk:DataGridTemplateColumn.CellTemplate>
 <DataTemplate>
 <Grid ToolTipService.ToolTip="Подробно">
 <sdk:Label Unloaded="Label_Unloaded" HorizontalAlignment="Center" Foreground="CornflowerBlue"  VerticalAlignment="Center" Content="+"></sdk:Label>
 <Border Background="Transparent" MouseLeftButtonDown="CheckBox_Click">
 </Border>
 </Grid>
 </DataTemplate>
 </sdk:DataGridTemplateColumn.CellTemplate>
 </sdk:DataGridTemplateColumn>
 </sdk:DataGrid.Columns>

 private void CheckBox_Click(object sender, RoutedEventArgs e)
        {
            // the original source is what was clicked. For example
            // a button.
            DependencyObject dep = (DependencyObject)e.OriginalSource;

            // iteratively traverse the visual tree upwards looking for
            // the clicked row.
            while ((dep != null) && !(dep is DataGridRow))
            {
                dep = VisualTreeHelper.GetParent(dep);
            }
            // if we found the clicked row
            if (dep != null && dep is DataGridRow)
            {
                // get the row
                DataGridRow row = (DataGridRow)dep;

                // change the details visibility
                if (row.DetailsVisibility == Visibility.Collapsed)
                {
                    row.DetailsVisibility = Visibility.Visible;
                }
                else
                {
                    row.DetailsVisibility = Visibility.Collapsed;
                }
            }
        }