[VB.NET]关于多线程和截图保存的问题!

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关于多线程和截图保存的问题!
问题是这样的,以下的几行代码,如果我在form_load事件中就能正常运行,而当我用多线程,单独创建一个线程运行时,老是会在第四行处,提示"未将对像引用设置到对像实例" 请问,,这到底是怎么回事呢?

My.Computer.Keyboard.SendKeys("^{prtsc}", True)
Dim img As Image
img = My.Computer.Clipboard.GetImage
img.Save("c:/tmp.jpg", System.Drawing.Imaging.ImageFormat.Jpeg)
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问题是这样的,以下的几行代码,如果我在form_load事件中就能正常运行,而当我用多线程,单独创建一个线程运行时,老是会在第四行处,提示"未将对像引用设置到对像实例" 请问,,这到底是怎么回事呢?

My.Computer.Keyboard.SendKeys("^{prtsc}", True)
Dim img As Image
img = My.Computer.Clipboard.GetImage
img.Save("c:/tmp.jpg", System.Drawing.Imaging.ImageFormat.Jpeg)
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晕啊....沉得这么快..自己顶上去先...
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晕死...没人回答呀....
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你的操作跨线程操作了，用委托。
Delegate Sub t1()
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim thread As New Thread(AddressOf test)
thread.Start()
End Sub
Sub test()
Me.BeginInvoke(New t1(AddressOf t2))
End Sub
Sub t2()
My.Computer.Keyboard.SendKeys("^{prtsc}", True)
Dim img As Image
img = My.Computer.Clipboard.GetImage
img.Save("c:/tmp.jpg", System.Drawing.Imaging.ImageFormat.Jpeg)
End Sub
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