Silverlight下TextBlock文字居中对齐的实现

.xaml

< Canvas
     xmlns ="http://schemas.microsoft.com/client/2007"
    xmlns:x ="http://schemas.microsoft.com/winfx/2006/xaml"
    Width ="640"  Height ="480"
    Background ="White"
    x:Name ="Page"
     >
   < Canvas  Width ="50"  Height ="26"  x:Name ="Do_Button"  Canvas.Left ="35"  Canvas.Top ="11" >
     < Rectangle  Width ="50"  Height ="26"  Stroke ="#FF212121"  RadiusX ="5"  RadiusY ="5"  StrokeThickness ="2"  x:Name ="RecProgressBg" >
       < Rectangle.Fill >
         < LinearGradientBrush  EndPoint ="0.5,1.167"  StartPoint ="0.5,-0.333" >
           < GradientStop  Color ="#0A0809"  Offset ="0" />
           < GradientStop  Color ="#0A0809"  Offset ="1" />
           < GradientStop  Color ="#666666"  Offset ="0.572" />
           < GradientStop  Color ="#0A0809"  Offset ="0.572" />
         </ LinearGradientBrush >
       </ Rectangle.Fill >
     </ Rectangle >
     < TextBlock  x:Name ="txtProgress"  Width ="100"  Height ="26"  Canvas.Left ="6"  Canvas.Top ="3"  TextWrapping ="NoWrap" >
     </ TextBlock >
   </ Canvas >   
</ Canvas >

.xaml.js

         var  txtProgress = rootElement.findName( " txtProgress " );
        txtProgress.foreground = " white " ;
        txtProgress.Text  = " 4/5 " ;
        txtProgress.FontSize = " 12 " ;
        txtProgress.FontWeight = " Thin " ;
         var  RecProgressBg = rootElement.findName( " RecProgressBg " );
        txtProgress.SetValue( " Canvas.Left " ,(RecProgressBg.Width - txtProgress.ActualWidth) / 2); // 居中对齐实现