WPF中如何使用行為示例：Canvas控件拖放行為的演示

1、獲取行為的支持，安裝Expression Blend 4 SDK（http://www.microsoft.com/zh-cn/download/details.aspx?id=10801） 。

2、創建行為庫

（1）創建一個Class Project，添加WPF必備的以及WPF中支持行為必備的dll文件。

其中，System.Windows.Interactivity.dll組件在目錄（需要安裝Blend SDKs）：C:\Program Files (x86)\Microsoft SDKs\Expression\Blend\.NETFramework\v4.0\Libraries。

（2）創建DragInCanvasBehavior.cs，繼承類Behavior<UIElement>，overrideBehavior<UIElement>得OnAttached()和OnDetaching()方法，代碼如下：

protected override void OnAttached()
        {
            base.OnAttached();
            this.AssociatedObject.MouseLeftButtonDown += AssociatedObject_MouseLeftButtonDown;
            this.AssociatedObject.MouseLeftButtonUp += AssociatedObject_MouseLeftButtonUp;
            this.AssociatedObject.MouseMove += AssociatedObject_MouseMove;
        }
    
        /// <summary>
        /// Behavior.OnDetaching()，移出事件處理程序
        /// </summary>
        protected override void OnDetaching()
        {
            base.OnDetaching();
            this.AssociatedObject.MouseLeftButtonDown -= AssociatedObject_MouseLeftButtonDown;
            this.AssociatedObject.MouseLeftButtonUp -= AssociatedObject_MouseLeftButtonUp;
            this.AssociatedObject.MouseMove -= AssociatedObject_MouseMove;
        }

（3）添加的行為的事件處理程序

private void AssociatedObject_MouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
        {
            if (canvas == null)
            {
                canvas = VisualTreeHelper.GetParent(this.AssociatedObject) as Canvas;
            }
            if (canvas != null)
            {
                isDragging = true;
                mouseOffset = e.GetPosition(this.AssociatedObject);
                AssociatedObject.CaptureMouse();
            }
        }
    
        private void AssociatedObject_MouseMove(object sender, System.Windows.Input.MouseEventArgs e)
        {
            if (canvas != null && isDragging == true)
            {
                Point p = e.GetPosition(canvas);
                AssociatedObject.SetValue(Canvas.TopProperty, p.Y - mouseOffset.Y);
                AssociatedObject.SetValue(Canvas.LeftProperty, p.X - mouseOffset.X);
            }
        }
    
        private void AssociatedObject_MouseLeftButtonUp(object sender, System.Windows.Input.MouseButtonEventArgs e)
        {
            if (isDragging)
            {
                AssociatedObject.ReleaseMouseCapture();
                isDragging = false;
            }
        }

（4）使用行為

在WPF Application中添加Class Library和System.Windows.Interactivity.dll

① 添加XML映射名稱空間

② 使用代碼

<Canvas >
        <Label x:Name="label" Content="我是中國人" Background="LemonChiffon" Width="240" HorizontalContentAlignment="Center" FontSize="16">
            <i:Interaction.Behaviors>
               <custom:DragInCanvasBehavior></custom:DragInCanvasBehavior>
            </i:Interaction.Behaviors>
        </Label>
        <Label x:Name="label2" Content="我是中國人" Background="LemonChiffon" Width="240" HorizontalContentAlignment="Center" FontSize="16">
            <i:Interaction.Behaviors>
                <custom:DragInCanvasBehavior></custom:DragInCanvasBehavior>
            </i:Interaction.Behaviors>
        </Label>
    </Canvas>

（5） 運行效果

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