爲什麼Canvas.SetTop動畫無法正常工作？

Question

我有這樣的XAML：

<Canvas Width="75" Height="75"> 
     <Button x:Name="button" Background="Olive" Canvas.Left="0" Canvas.Top="0" Width="75" Height="75" Click="button_Click"/> 
    </Canvas> 

而這後面的代碼：

Private Sub button_Click(ByVal sender as Object, ByVal e as System.Windows.RoutedEventArgs) 
     Canvas.SetTop(sender, -75) 

     Dim sb1 As New Storyboard 
     Dim da1 As New DoubleAnimationUsingKeyFrames 
     da1.BeginTime = TimeSpan.FromSeconds(0) 
     Storyboard.SetTargetName(da1, CType(sender, Button).Name) 
     Storyboard.SetTargetProperty(da1, New PropertyPath(Canvas.TopProperty)) 

     Dim t1 As Double = Canvas.GetTop(sender) 
     da1.KeyFrames.Add(New SplineDoubleKeyFrame(t1 + 75, TimeSpan.FromSeconds(0.2))) 
     sb1.Children.Add(da1) 

     BeginStoryboard(sb1)   
    End Sub 

當我點擊按鈕的第一次，它恰當地75上升，以動畫方式返回0，但是當我再次點擊該按鈕，它會將動畫縮小75.爲什麼它跳過Canvas.SetTop線並直接進入動畫部分？以及如何解決這個問題？

Answer 1

使用該代碼（這是在C＃）之前Canvas.SetTop

(sender as UIElement).BeginAnimation(Canvas.TopProperty, null); 

這將避免任何動畫覆蓋值Canvas.TopProperty

此鏈接將幫助您

http://joshsmithonwpf.wordpress.com/2008/08/21/removing-the-value-applied-by-an-animation/