动态向DataTemplate添加控件？

<DataTemplate x:Name="cmbTemplate">
<Grid Height="auto" Width="auto">
<Grid.RowDefinitions >
<RowDefinition Height="10"/>
    <RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid Grid.Row="0" HorizontalAlignment="Right">
<Image  Name="tipClose"  MouseLeftButtonUp="tipClose_MouseLeftButtonUp"   Source="../image/close.jpg"/>
</Grid>
<Grid Grid.Row="1">
<sdk:TabControl >
<sdk:TabItem Header="ABC">
<Grid Name="Grid_StreetManage"> </Grid>
</sdk:TabItem>
                                                                                     
</sdk:TabControl>
</Grid>
</Grid>
</DataTemplate>
请问怎么通过后台程序（C#）将后台的TextBlock添加到Grid_StreetManage中？
通过以下方法无果！
Grid panel = (Grid)this.cmbTemplate.LoadContent();
Grid tbCategory = panel.FindName("Grid_StreetManage") as Grid;TextBlock tex = new TextBlock();
tex.Text = "asdklfja;sdf";
tex.SetValue(Grid.VerticalAlignmentProperty, VerticalAlignment.Center);
tex.SetValue(Grid.HorizontalAlignmentProperty, HorizontalAlignment.Center);
tex.SetValue(Grid.RowProperty, 0);
tex.SetValue(Grid.ColumnProperty, 0);
tbCategory.Children.Add(tex);通过以下这种方法也有很多不对的，不能添加事件，而且经常会出错之类
 StringBuilder CellETemp = new StringBuilder();
CellETemp.Append("<DataTemplate ");请问哪位知道要怎么处理呢？谢谢