[Solved with Solution] Prevent picturebox from repainting

Ok that doesn't work for me ...
I made it like this:

public void paintpicture(int tabnummer)
{

int w = 390 - 1, h = 390 - 1;

Bitmap bitmap = new Bitmap(w,h, System.Drawing.Imaging.PixelFormat.Format32bppArgb);

Graphics bmpgrafik = Graphics.FromImage(bitmap);

bmpgrafik.CompositingMode = CompositingMode.SourceCopy;
bmpgrafik.CompositingQuality = CompositingQuality.HighQuality;
try{
  bmpgrafik.FillRectangle(new SolidBrush(notenfarbe), x + w / 2 - dotstrength, y * -1 + h / 2 - dotstrength, dotstrength * 2 + 1, dotstrength * 2 + 1);
}catch(Exception error)
{
;
}

imagepreview[tabnummer].Image = bitmap;
bitmap.Dispose();
bmpgrafik.Dispose();
}

It only shows a red cross. I searched and google says that it could be a paint exception.
But it never throws out an exception...

If I made it in the paint event with 
grafik.DrawImage(bitmap, 0, 0, bitmap.Width, bitmap.Height);
Where grafik is Graphics grafik = e.Graphics
instead of imagepreview[tabnummer].Image = bitmap;
it works normal

I really want it working. Have you an other idea?
Thanks


Edit: Something that work too is to save the bitmap first into a file and the load it with Image.FromFile(filename);
But thats not really optimal... 


Solution: Sorry that I said your tipp didn't work.
I was just that stupid and disposed the bitmap directly after setting it up :D
So the code above works perfectly if you leave out bitmap.dispose();