使用ObjectAnimationUsingKeyFrames来控制图像幻灯片

Question

我正在尝试使用动画来控制图像的幻灯片。

用户在txtaddress中输入文件夹路径，点击btnGo，程序会在该文件夹中显示每个图像两秒钟。

然而，我正在利用动画来控制这一点。当它开始幻灯片放映时，我收到错误“无法解析属性路径中的所有属性引用”imgMain.Source“

我的完整代码如下。有什么想法吗？

Imports System.IO
Imports System.Windows.Media.Animation

Class MainWindow

    Private Property ImageSource As String

    Private Sub btnGo_Click(sender As System.Object, e As System.Windows.RoutedEventArgs) Handles btnGo.Click
        'Get file list
        Dim fileList(0) As String
        Dim btm(0) As BitmapImage
        Dim dir1 As New DirectoryInfo(txtAddress.Text)
        Dim anim As New ObjectAnimationUsingKeyFrames

        For Each fi In dir1.GetFiles("*.bmp")
            fileList(UBound(fileList)) = fi.Name
            ReDim Preserve fileList(UBound(fileList) + 1)
        Next

        For Each fi In dir1.GetFiles("*.png")
            fileList(UBound(fileList)) = fi.Name
            ReDim Preserve fileList(UBound(fileList) + 1)
        Next

        For Each fi In dir1.GetFiles("*.jpg")
            fileList(UBound(fileList)) = fi.Name
            ReDim Preserve fileList(UBound(fileList) + 1)
        Next

        'Create animation
        anim.Duration = TimeSpan.FromSeconds(UBound(fileList) * 2)

        Dim idx As Integer
        For idx = 0 To UBound(fileList) - 1
            btm(idx) = New BitmapImage(New Uri(txtAddress.Text & "\" & fileList(idx), UriKind.Absolute))
            anim.KeyFrames.Add(New DiscreteObjectKeyFrame(btm(idx), KeyTime.FromTimeSpan(TimeSpan.FromSeconds(idx * 2))))
            ReDim Preserve btm(UBound(btm) + 1)
        Next

        Dim sBoard As New Storyboard
        sBoard.Children.Add(anim)
        Storyboard.SetTargetName(anim, imgMain.Name)
        Storyboard.SetTargetProperty(anim, New PropertyPath("imgMain.Source"))
        sBoard.Begin(Me)
    End Sub

End Class