C#-Code:

public delegate bool CallBack(int hwnd, int lParam); 


public class EnumReportApp { 


    [DllImport("user32")]
    public static extern int EnumWindows(CallBack x, int y); 


    public static void Main() 
    {
        CallBack myCallBack = new CallBack(EnumReportApp.Report);
        EnumWindows(myCallBack, 0);
    } 


   public static bool Report(int hwnd, int lParam) { 
        Console.Write("Window handle is ");
        Console.WriteLine(hwnd);
        return true;
    }
}