PresentationCore.dll中发生'System.NullReferenceException'

Question

我不知道该怎么办！我正在尝试在后台线程中运行OpenCV并让它将图像发送给调度程序。这是代码的（蒸馏）版本：

private Thread _thread
private void WindowLoaded(){
   _thread = new Thread(new ThreadStart(OpenCV)); //Run in seperate thread
   _thread.Start();
}
private void OpenCV(){
   //CV Image Capturing and parsing etc - works fine!
   //...

   //Problems begin
   System.Drawing.Bitmap bm = BitmapConverter.ToBitmap(gray); //Get a usable image from CV
   bm.SetResolution(640.0f, 480.0f); //Change its resolution
   Dispatcher.BeginInvoke(new Action(() => { //Invoke this to be run in main thread
       updateImage(bm); //Code that updates UI
   }));
}
private void updateImage(System.Drawing.Bitmap img) {
    ImageSourceConverter c = new ImageSourceConverter(); 
    //Console.WriteLine(c == null); //No success in testing for nulls!
    MyImage.Source = (ImageSource)c.ConvertFrom(img); //The problem is here
}

在updateImage的最后一行标题中的错误发生了。我见过许多其他人遇到过非常相似的问题，但他们的解决方案似乎都没有用。

调用异常时，MyImage不为null，也不是c或img。但是，MyImage.Source是。