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EnumWindows (user32)

C# Signature:

[return: MarshalAs(UnmanagedType.Bool)]
static extern bool EnumWindows(EnumWindowsProc lpEnumFunc, IntPtr lParam);

User-Defined Types:



Callback EnumWindowsProc should return true to continue enumerating or false to stop.

Tips & Tricks:

The corresponding unmanaged return type is a 4-byte Win32 'BOOL', so mark the method with the MarshalAsAttribute(UnmanagedType.Bool).

Great sample using managed code and a delegate type for the call back from MSDN:


using System.Runtime.InteropServices;

public delegate bool CallBackPtr(int hwnd, int lParam);
private CallBackPtr callBackPtr;

public class EnumReport
    private static extern int EnumWindows(CallBackPtr callPtr, int lPar);

    public static bool Report(int hwnd, int lParam)
        Console.WriteLine("Window handle is "+hwnd);
        return true;
static void Main()

     // note in other situations, it is important to keep
     // callBackPtr as a member variable so it doesnt GC while you're calling EnumWindows

     callBackPtr = new CallBackPtr(EnumReport.Report);  
    EnumReport.EnumWindows(callBackPtr, 0);

Alternative Managed API:

The ManagedWindowsApi project ( provides a static

method ManagedWinapi.Windows.SystemWindow.FilterToplevelWindows().

EnumWindows on MSDN

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