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I am working on a CCTV project which employs ONVIF. I use a Winform sample, which is provided by "ONVIF Device Manager" project, to obtain video frames from a camera. (You can find it here)
It was working fine if I connect to one camera. But, if I connect to six cameras some picture box does not redraw when I assign new images in DrawFrame(). Two back rectangles contain a red ellipse in the attached picture are supposed to display an image. This issues only occur when picture box size mode is Zoom. As what I have tried, those picture boxes can only redraw if I call Application.DoEvent() or call PictureBox.Update()/Refresh() every time when I set a new image.

Two red ellipses in the attached picture are supposed to display an image

private void DrawFrame(VideoBuffer videoBuffer, PlaybackStatistics statistics)

 Bitmap bmp = img as Bitmap;
 BitmapData bd = null;
 try
 
 bd = bmp.LockBits(new System.Drawing.Rectangle(0, 0, bmp.Width, bmp.Height), System.Drawing.Imaging.ImageLockMode.WriteOnly, System.Drawing.Imaging.PixelFormat.Format32bppArgb);//bgra32

 using (var md = videoBuffer.Lock())
 

 CopyMemory(bd.Scan0, md.value.scan0Ptr, videoBuff.stride * videoBuff.height);

 //bitmap.WritePixels(
 // new Int32Rect(0, 0, videoBuffer.width, videoBuffer.height),
 // md.value.scan0Ptr, videoBuffer.size, videoBuffer.stride,
 // 0, 0
 //);
 

 
 catch (Exception err)
 
 //errBox.Text = err.Message;
 Debug.Print("DrawFrame:: " + err.Message);
 
 finally
 
 bmp.UnlockBits(bd);
 
 imageBox.Image = bmp;
 /*Application.DoEvent() // not recommended since this method causes the current thread to be suspended
 or call imageBox.Update() // causes hanging on UI thread
 or imageBox.Refresh() // causes hanging on UI thread
 or PictureBox.Invalidate(), do nothing.*/

I create picture boxes and add to a panel following this code.

PictureBox ptBox = new PictureBox();
ptBox.Size = new Size(elementWidth, elementHeight);
ptBox.Name = "PictureBox_" + (j) + (i);
ptBox.Location = new Point(j * elementWidth, i * elementHeight); //relative location
ptBox.BorderStyle = BorderStyle.FixedSingle;
ptBox.SizeMode = PictureBoxSizeMode.Zoom;
mPanel.Controls.Add(ptBox);

After a week, I found that PictureBoxs occurs the error does not trigger OnPaint(PaintEventArgs e) event. It leads to the error that new images are not redrawn.