Silverlight实现的简单拖拽效果

MainPage.xaml文件代码：

<UserControl

 x:Class="SilverlightApplication2.MainPage"

 Width="640" Height="480">

 <Canvas x:Name="LayoutRoot" Background="White">

  <StackPanel MouseLeftButtonDown="OnMouseDown" MouseMove="OnMouseMove" MouseLeftButtonUp="OnMouseLeftButtonUp" Width="200" Height="80" Canvas.Left="20" Canvas.Top="20">

   <Border BorderBrush="Red" BorderThickness="3">

    <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center">

     <Image Source="qq.gif"/>

     <TextBlock Text="拖动"  Margin="20" VerticalAlignment="Center"/>

    </StackPanel>

   </Border>

  </StackPanel>

  <TextBlock x:Name="status" Canvas.Top="200" Text="" Canvas.Left="60"></TextBlock>

 </Canvas>

</UserControl>

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MainPage.xaml.cs文件如下：

using System;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Documents;

using System.Windows.Ink;

using System.Windows.Input;

using System.Windows.Media;

using System.Windows.Media.Animation;

using System.Windows.Shapes;

namespace SilverlightApplication2

{

 public partial class MainPage : UserControl

 {

  public MainPage()

  {

   // 为初始化变量所必需

   InitializeComponent();

  }

  //定义两个全局变量，一个用来获取鼠标的当前位置，另一个用来记录鼠标是否移动

  bool trackingMouseMove = false;

  Point mousePosition;

  private void OnMouseDown(object sender, System.Windows.Input.MouseButtonEventArgs e)

   // TODO: Add event handler implementation here.

   FrameworkElement element = sender as FrameworkElement;

   mousePosition = e.GetPosition(null);

   trackingMouseMove = true;

   if(null!=null)

   {

    element.CaptureMouse();

    element.Cursor = Cursors.Hand;

   }

   status.Text = "按下鼠标";

  private void OnMouseLeftButtonUp(object sender, System.Windows.Input.MouseButtonEventArgs e)

   trackingMouseMove = false;

   element.ReleaseMouseCapture();

   mousePosition.X = mousePosition.Y = 0;

   element.Cursor = null;

   status.Text = "鼠标释放";

  private void OnMouseMove(object sender, System.Windows.Input.MouseEventArgs e)

   if(trackingMouseMove)

    double deltaV = e.GetPosition(null).Y-mousePosition.Y;

    double deltaH = e.GetPosition(null).X-mousePosition.X;

    double newTop = deltaV+(double)element.GetValue(Canvas.TopProperty);

    double newLeft = deltaH+(double)element.GetValue(Canvas.LeftProperty);

    element.SetValue(Canvas.TopProperty,newTop);

    element.SetValue(Canvas.LeftProperty,newLeft);

    mousePosition = e.GetPosition(null);

   status.Text = "鼠标移动中";

 }

}