public partial class Form1 : Form
{
  [DllImport("coredll.dll")]
  static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);

  const int GWL_WNDPROC = -4;

  public delegate int WindProc(IntPtr hWnd, uint msg, long Wparam, long lparam);

    public Form1()
    {
        InitializeComponent();

        WindProc SampleProc = new WindProc (SubclassWndProc);

        SetWindowLong(this .Handle , GWL_WNDPROC,
            SampleProc.Method .MethodHandle.Value.ToInt32());

    }

public int SubclassWndProc(IntPtr  hwnd, uint  msg, long  Wparam, long  lparam)
{
    return 1;
}

Here is the sample which i was trying to take the window procedure of a form, this is how i do in C++ i get the windwproc easlily if i try the same in C# .net 3.5 i am unable to get the window proc,, after calling SetWindowLong API application hangs and it pops up some dont send report... i have read this is the way to get the window proc.. please let me know were i am making mistake...