Silverlight自动根据屏幕分辨率进行布局

xaml：

<UserControl x:Class="SLCenterLayout.MainPage"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
     mc:Ignorable="d"
     d:DesignHeight="" d:DesignWidth="" x:Name="ControlMainPage" >
     <UserControl.Resources>     </UserControl.Resources>
     <UserControl.RenderTransform>
         <CompositeTransform />
     </UserControl.RenderTransform>     <ScrollViewer x:Name="LayoutRoot" MaxWidth="" MaxHeight=""VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto" Background="Black">
      <Grid HorizontalAlignment="Center">
             <Grid.RowDefinitions>
                 <RowDefinition />
                 <RowDefinition />
             </Grid.RowDefinitions>
             <Image Source="2.jpg"/>
             <TextBlock Grid.Row="" FontSize="" Foreground="White">小米手机快发货啊</TextBlock>
         </Grid>
     </ScrollViewer>
 </UserControl>

xaml.cs:

using System;
using System.Windows.Controls;
using System.Windows.Media;namespace SLCenterLayout
 {
     public partial class MainPage : UserControl
     {
         //标准显示宽度
        private const double RECOMMAND_SCREEN_WIDTH = ;         //标准显示高度
        private const double RECOMMAND_SCREEN_HEIGHT = ;         public MainPage()
         {
             InitializeComponent();
             App.Current.Host.Content.Resized+=new EventHandler(Content_Resized);
         }         private void ChangePageRenderSize(double currentWidth, double currentHeight)
         {
             if (currentWidth > RECOMMAND_SCREEN_WIDTH || currentHeight > RECOMMAND_SCREEN_HEIGHT)
             {
                 CompositeTransform ctf = new CompositeTransform();
                 ctf.ScaleX = currentWidth / RECOMMAND_SCREEN_WIDTH;
                 ctf.ScaleY = currentHeight / RECOMMAND_SCREEN_HEIGHT;                 //沿着中心点进行缩放，这样的话，在多次缩放后，不会偏移原来位置
                ctf.CenterX = currentWidth / ;
                 ctf.CenterY = currentHeight / ;
                 ControlMainPage.RenderTransform = ctf;
             }
         }         private void Content_Resized(object sender, EventArgs e)
         {
             ChangePageRenderSize(ControlMainPage.ActualWidth, ControlMainPage.ActualHeight);
         }     }