InvalidOperationException - object is currently in use elsewhere - red cross

Question

This is because Gdi+ Image class is not thread safe. Hovewer you can avoid InvalidOperationException by using lock every time when you need to Image access, for example for painting or getting image size:

Image DummyImage;

// Paint
lock (DummyImage)
    e.Graphics.DrawImage(DummyImage, 10, 10);

// Access Image properties
Size ImageSize;
lock (DummyImage)
    ImageSize = DummyImage.Size;

BTW, invocation is not needed, if you will use the above pattern.

I had a similar problem with the same error message but try as I might, locking the bitmap didn't fix anything for me. Then I realized I was drawing a shape using a static brush. Sure enough, it was the brush that was causing the thread contention.

var location = new Rectangle(100, 100, 500, 500);
var brush = MyClass.RED_BRUSH;
lock(brush)
    e.Graphics.FillRectangle(brush, location);

This worked for my case and lesson learned: Check all the reference types being used at the point where thread contention is occurring.

Seems to me, that the same Camera object is used several times.

E.g. try to use a new buffer for each received frame. It seems to me, that while the picture box is drawing the new frame, your capture library fills that buffer again. Therefore on faster machines this might not be an issue, with slower machines it might be an issue.

I've programmed something similar once, after each received frame, we had to request to receive the next frame and set the NEW frame receive buffer in that request.

If you can not do that, copy the received frame from the camera first to a new buffer and append that buffer to a queue, or just use 2 alternating buffers and check for overruns. Either use myOutPutPanel.BeginInvoke to call the camera_ReceivedFrame method, or better have a thread running, which checks the queue, when it has a new entry it calls mnyOutPutPanel.BeginInvoke to invoke your method to set the new buffer as image on the panel.

Furthermore, once you received the buffer, use the Panel Invoke Method to invoke the setting of the image (guarantee that it runs in the window thread and not the thread from your capture library).

The example below can be called from any thread (capture library or other separate thread):

void camera_ReceivedFrame(object sender, StreamEventArgs e)
{
    if(myOutputPanel.InvokeRequired)
    {
        myOutPutPanel.BeginInvoke( 
            new Camera.ReceivedFrameEventHandler(camera_ReceivedFrame), 
            sender, 
            e);
    }
    else
    {
        myOutPutPanel.Image = e.Image;
    }
}