C# Signature:

[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool EnumWindows(EnumWindowsProc lpEnumFunc, IntPtr lParam);

User-Defined Types:

EnumWindowsProc

Notes:

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:

http://msdn2.microsoft.com/en-us/library/d186xcf0(VS.71).aspx

SAMPLE CODE!!

using System.Runtime.InteropServices;

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

public class EnumReport
{
    [DllImport("user32.dll")]
    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 (http://mwinapi.sourceforge.net) provides a static

method ManagedWinapi.Windows.SystemWindow.FilterToplevelWindows().

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