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Posted 11 Oct 2002


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Capturing the Screen Image in C#

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4.57/5 (37 votes)
27 Feb 2003
An article on capturing the Screen using Win32 APIs in C#

Image 1


I am working on a desktop sharing type application in C#. First problem that I encountered was that there was not much in C# to capture the desktop image. After a bit of research I came to know that I shall have to use the Win32 APIs to provide this functionality to my application. I made following three classes to perform this job.

  1. PlatformInvokeGDI32: All the GDI32.dll APIs being used in this application are placed in this class.
  2. PlatformInvokeUSER32: All the User32.dll APIs have been placed in this class.
  3. CaptureScreen: In this class I have provided a simple static function GetDesktopImage that captures the screen image using the APIs  given in PlatformInvokeGDI32 and PlatformInvokeUSER32 and returns it as a bitmap.

You can very easily place these classes in your C# application. Just copy and paste following code in your C# project without changing any thing at all. If you want to use accompanying source files, you can  add the CaptureScreen namespace in your project or just change the CaptureScreen namespace in these classes with your project namespace and that's all.

The beautiful source code

/// <summary>
/// This class shall keep the GDI32 APIs used in our program.
/// </summary>
public class PlatformInvokeGDI32
#region Class Variables
    public const int SRCCOPY = 13369376;
#region Class Functions<br>
    public static extern IntPtr DeleteDC(IntPtr hDc);

    public static extern IntPtr DeleteObject(IntPtr hDc);

    public static extern bool BitBlt(IntPtr hdcDest,int xDest,
        int yDest,int wDest,int hDest,IntPtr hdcSource,
        int xSrc,int ySrc,int RasterOp);

    [DllImport ("gdi32.dll",EntryPoint="CreateCompatibleBitmap")]
    public static extern IntPtr CreateCompatibleBitmap(IntPtr hdc,
        int nWidth, int nHeight);

    [DllImport ("gdi32.dll",EntryPoint="CreateCompatibleDC")]
    public static extern IntPtr CreateCompatibleDC(IntPtr hdc);

    [DllImport ("gdi32.dll",EntryPoint="SelectObject")]
    public static extern IntPtr SelectObject(IntPtr hdc,IntPtr bmp);

#region Public Constructor

/// <summary>
/// This class shall keep the User32 APIs used in our program.
/// </summary>
public class PlatformInvokeUSER32
#region Class Variables
    public const int SM_CXSCREEN=0;
    public const int SM_CYSCREEN=1;

#region Class Functions
    [DllImport("user32.dll", EntryPoint="GetDesktopWindow")]
    public static extern IntPtr GetDesktopWindow();

    public static extern IntPtr GetDC(IntPtr ptr);

    public static extern int GetSystemMetrics(int abc);

    public static extern IntPtr GetWindowDC(Int32 ptr);

    public static extern IntPtr ReleaseDC(IntPtr hWnd,IntPtr hDc);


/// <summary>
/// This class shall keep all the functionality 
/// for capturing the desktop.
/// </summary>
public class CaptureScreen
#region Class Variable Declaration
    protected static IntPtr m_HBitmap;

/// This class shall keep all the functionality for capturing
/// the desktop.
public class CaptureScreen
  #region Public Class Functions
  public static Bitmap GetDesktopImage()
    //In size variable we shall keep the size of the screen.
    SIZE size;

    //Variable to keep the handle to bitmap.
    IntPtr hBitmap;

    //Here we get the handle to the desktop device context.
    IntPtr  hDC = PlatformInvokeUSER32.GetDC

    //Here we make a compatible device context in memory for screen
    //device context.
    IntPtr hMemDC = PlatformInvokeGDI32.CreateCompatibleDC(hDC);

    //We pass SM_CXSCREEN constant to GetSystemMetrics to get the
    //X coordinates of the screen. = PlatformInvokeUSER32.GetSystemMetrics

    //We pass SM_CYSCREEN constant to GetSystemMetrics to get the
    //Y coordinates of the screen. = PlatformInvokeUSER32.GetSystemMetrics

    //We create a compatible bitmap of the screen size and using
    //the screen device context.
    hBitmap = PlatformInvokeGDI32.CreateCompatibleBitmap

    //As hBitmap is IntPtr, we cannot check it against null.
    //For this purpose, IntPtr.Zero is used.
    if (hBitmap!=IntPtr.Zero)
      //Here we select the compatible bitmap in the memeory device
      //context and keep the refrence to the old bitmap.
      IntPtr hOld = (IntPtr) PlatformInvokeGDI32.SelectObject
                             (hMemDC, hBitmap);
      //We copy the Bitmap to the memory device context.
      PlatformInvokeGDI32.BitBlt(hMemDC, 0, 0,,, hDC,
                                 0, 0,PlatformInvokeGDI32.SRCCOPY);
      //We select the old bitmap back to the memory device context.
      PlatformInvokeGDI32.SelectObject(hMemDC, hOld);
      //We delete the memory device context.
      //We release the screen device context.
                                     GetDesktopWindow(), hDC);
      //Image is created by Image bitmap handle and stored in
      //local variable.
      Bitmap bmp = System.Drawing.Image.FromHbitmap(hBitmap); 
      //Release the memory to avoid memory leaks.
      //This statement runs the garbage collector manually.
      //Return the bitmap 
      return bmp;
    //If hBitmap is null, retun null.
    return null;

//This structure shall be used to keep the size of the screen.
public struct SIZE
    public int cx;
    public int cy;


The demo application with this code shows the use of these classes. Its a very simple windows application in which there is a simple form having a menu and a picture box control. Capture Screen menu item of menu is used to capture the screen and assign to the image property of picture box control. I hope you like this code. I have commented each line of this code to make it self explanatory. If there is still something confusing for you, please let me know. Good Luck!


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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About the Author

Agha Ali Raza
Web Developer
Pakistan Pakistan
No Biography provided

Comments and Discussions

GeneralRe: Major Memory Leak Pin
Jisu7411-Nov-05 13:51
MemberJisu7411-Nov-05 13:51 
GeneralRe: Major Memory Leak Pin
Gavin Kendall21-May-09 4:46
professionalGavin Kendall21-May-09 4:46 
GeneralRe: Major Memory Leak Pin
jdohnoe7-Apr-10 14:36
Memberjdohnoe7-Apr-10 14:36 
Generalthe Dll functions Pin
tokyo_bme2-Mar-05 8:36
Membertokyo_bme2-Mar-05 8:36 
GeneralRe: the Dll functions Pin
jjreilly2-Mar-05 9:18
Memberjjreilly2-Mar-05 9:18 
GeneralRe: the Dll functions Pin
tokyo_bme4-Mar-05 21:30
Membertokyo_bme4-Mar-05 21:30 
Generalscreen capture in web app Pin
eheuer17-Feb-05 3:34
Membereheuer17-Feb-05 3:34 
GeneralRe: screen capture in web app Pin
Timmy237-Mar-05 22:25
MemberTimmy237-Mar-05 22:25 
I'm having the exact same problem,
however, I found out what the cause is.

If you execute a shell command from your .NET webapp,
the shell is executed within the account ASPNET,
and if you look under your running processes you see the
shell is executed but as a "NETWORK SERVICE". Unsure | :~

I'm looking for something to execute a shell
under the user-account and not as an ASPNET-service.

The shell I'm referring to could be a screencapture-application
which saves a screenshot to your webroot.

Anyway, anybody has some more experience??
GeneralBug with multiple monitors Pin
Sherrod Segraves24-Sep-04 6:52
MemberSherrod Segraves24-Sep-04 6:52 
GeneralBlack screen???Help!!!!!!! Pin
WalkWorld5-Sep-04 20:05
MemberWalkWorld5-Sep-04 20:05 
GeneralRe: Black screen???Help!!!!!!! Pin
deonvs28-Jul-09 14:59
Memberdeonvs28-Jul-09 14:59 
QuestionOverlay? Pin
Jakub Florczyk22-Jul-03 23:59
MemberJakub Florczyk22-Jul-03 23:59 
GeneralHelp with the remoting aspect Pin
UTAMav11-Jul-03 7:26
MemberUTAMav11-Jul-03 7:26 
GeneralRe: Help with the remoting aspect Pin
Agha Ali Raza26-Jul-03 14:12
MemberAgha Ali Raza26-Jul-03 14:12 
GeneralForm to bitmap (before it ever hits the screen) Pin
stantheman4-Mar-03 11:54
Memberstantheman4-Mar-03 11:54 
GeneralAn alternative method Pin
Orvindo4-Mar-03 10:04
MemberOrvindo4-Mar-03 10:04 
QuestionHow much fun is it too... Pin
Ryan Cromwell4-Mar-03 9:53
MemberRyan Cromwell4-Mar-03 9:53 
GeneralNot too shabby Pin
Richard Johnn1-Mar-03 20:01
MemberRichard Johnn1-Mar-03 20:01 
General1000th Version of "Hello World" Pin
Member 1174176228-Feb-03 10:30
MemberMember 1174176228-Feb-03 10:30 
GeneralRe: 1000th Version of "Hello World" Pin
Tomas Petricek28-Feb-03 12:32
MemberTomas Petricek28-Feb-03 12:32 
GeneralRe: 1000th Version of "Hello World" Pin
imaginejta1-Mar-03 6:23
Memberimaginejta1-Mar-03 6:23 
GeneralRe: 1000th Version of "Hello World" Pin
Thomas A. Dzieran2-Mar-03 13:42
MemberThomas A. Dzieran2-Mar-03 13:42 
GeneralSlow Hog Pin
Shawn Stevens28-Feb-03 9:34
MemberShawn Stevens28-Feb-03 9:34 
GeneralRe: Slow Hog Pin
flipdoubt2-Mar-03 6:13
Memberflipdoubt2-Mar-03 6:13 
GeneralRe: Slow Hog Pin
Shawn Stevens2-Mar-03 9:37
MemberShawn Stevens2-Mar-03 9:37 

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