Thanks to Pascal Cloup and John Hornick for discovering a memory leak in this code.

Capturing the screen or the surface of a control

This simple process requires a little bit of interop to provide access to the GDI BitBlt API.

First, you need to import the BitBlt, GetDC and ReleaseDC functions.

//imports the GDI BitBlt function that enables the background of the window

//to be captured

[DllImport("gdi32.dll")]

private static extern bool BitBlt(

IntPtr hdcDest, // handle to destination DC

int nXDest, // x-coord of destination upper-left corner

int nYDest, // y-coord of destination upper-left corner

int nWidth, // width of destination rectangle

int nHeight, // height of destination rectangle

IntPtr hdcSrc, // handle to source DC

int nXSrc, // x-coordinate of source upper-left corner

int nYSrc, // y-coordinate of source upper-left corner

System.Int32 dwRop // raster operation code

);

[DllImport("User32.dll")]

public extern static System.IntPtr GetDC(System.IntPtr hWnd);

[DllImport("User32.dll")]

public extern static int ReleaseDC(System.IntPtr hWnd, System.IntPtr hDC); //modified to include hWnd

Now, to capture the screen in it's entirety you can do the following.

System.IntPtr desktopDC=GetDC(System.IntPtr.Zero);

Bitmap bm=new Bitmap(SystemInformation.VirtualScreen.Width, SystemInformation.VirtualScreen.Height);

Graphics g=Graphics.FromImage(bm);

System.IntPtr bmDC=g.GetHdc();

BitBlt(bmDC,0,0,bm.Width,bm.Height,desktopDC,0,0,0x00CC0020 /*SRCCOPY*/);

ReleaseDC(System.IntPtr.Zero, desktopDC);

g.ReleaseHdc(bmDC);

g.Dispose();

The Bitmap object BM now contains a screen shot of the entire desktop.

To capture an individual control, for example the surface of a PictureBox you can do the following.

System.IntPtr srcDC=GetDC(this.pictureBox1.Handle);

Bitmap bm=new Bitmap(this.pictureBox1.Width,this.pictureBox1.Height);

Graphics g=Graphics.FromImage(bm);

System.IntPtr bmDC=g.GetHdc();

BitBlt(bmDC,0,0,bm.Width,bm.Height,srcDC,0,0,0x00CC0020 /*SRCCOPY*/);

ReleaseDC(this.pictureBox1.Handle, srcDC);

g.ReleaseHdc(bmDC);

g.Dispose();