[C #] failed to use bitblt in GDI + to draw the image to the window

The Code is as follows. Draw a graph to the window and the result is only a black rectangle:

1 Bitmap bmp = (Bitmap)Bitmap.FromFile(@"C:\Users\Ken\Desktop\Load2.bmp"); 
2 Graphics grDest = Graphics.FromHwnd(pictureBox1.Handle); 
3 Graphics grSrc = Graphics.FromImage(bmp); 
4 IntPtr hdcDest = grDest.GetHdc(); 
5 IntPtr hdcSrc = grSrc.GetHdc(); 
6 BitBlt(hdcDest, 0, 0, pictureBox1.Width, pictureBox1.Height, 
7     hdcSrc, 0, 0, (uint)TernaryRasterOperations.SRCCOPY); // 0x00CC0020 
8 grDest.ReleaseHdc(hdcDest); 
9 grSrc.ReleaseHdc(hdcSrc); 

Here, I want to use the raster-Operation Capability of bitblt to draw an image to graphics without using drawimage. Specifically, I have two images in my hand, one of them is a hidden color and requires and then the OR operation. Therefore, the bitblt of GDI must be used.

Solution:

 1 using (Bitmap bmp = (Bitmap)Bitmap.FromFile(@"C:\Jason\forest.jpg")) 
 2 using (Graphics grDest = Graphics.FromHwnd(pictureBox1.Handle)) 
 3 using (Graphics grSrc = Graphics.FromImage(bmp)) 
 4 { 
 5     IntPtr hdcDest = IntPtr.Zero; 
 6     IntPtr hdcSrc = IntPtr.Zero; 
 7     IntPtr hBitmap = IntPtr.Zero; 
 8     IntPtr hOldObject = IntPtr.Zero; 
 9     try 
10     { 
11         hdcDest = grDest.GetHdc(); 
12         hdcSrc = grSrc.GetHdc(); 
13         hBitmap = bmp.GetHbitmap(); 
14         hOldObject = SelectObject(hdcSrc, hBitmap); 
15         if (hOldObject == IntPtr.Zero)                 
16             throw new Win32Exception(); 
17         if (!BitBlt(hdcDest, 0, 0, pictureBox1.Width, pictureBox1.Height, hdcSrc, 0, 0, 0x00CC0020U))                 
18             throw new Win32Exception(); }
19     finally 
20     { 
21         if (hOldObject != IntPtr.Zero) SelectObject(hdcSrc, hOldObject); 
22         if (hBitmap != IntPtr.Zero) DeleteObject(hBitmap); 
23         if (hdcDest != IntPtr.Zero) grDest.ReleaseHdc(hdcDest); 
24         if (hdcSrc != IntPtr.Zero) grSrc.ReleaseHdc(hdcSrc); 
25     } 
26 } 

That is to say, before bitblt, select the bitmap associated with graphics as the DC background image.

Guess, use graphics. fromimage ,. at the bottom layer of net, the hbitmap corresponding to bitmap is not selected into HDC, but only two. net object, and then SelectObject is selected and selected twice in drawimage to draw on hbitmap. Therefore, when performing a GDI operation independently of. net, you need to associate the two at the GDI level and use SelectObject.