Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object
  at System.Windows.Forms.FileDialog..ctor () [0x000db] in /home/cvs/mcs/class/Managed.Windows.Forms/System.Windows.Forms/FileDialog.cs:124
  at System.Windows.Forms.OpenFileDialog..ctor () [0x00006] in /home/cvs/mcs/class/Managed.Windows.Forms/System.Windows.Forms/OpenFileDialog.cs:40
  at (wrapper remoting-invoke-with-check) System.Windows.Forms.OpenFileDialog:.ctor ()
  at testwin.MainForm.OnClick (System.Object sender, System.EventArgs e) [0x00000] in /home/cvs/winforms/filedialog/swf-filedialog.cs:36
  at (wrapper delegate-invoke) System.MulticastDelegate:invoke_void_object_EventArgs (object,System.EventArgs)
  at System.Windows.Forms.Control.OnClick (System.EventArgs e) [0x00018] in /home/cvs/mcs/class/Managed.Windows.Forms/System.Windows.Forms/Control.cs:4177
  at System.Windows.Forms.Button.OnClick (System.EventArgs e) [0x00031] in /home/cvs/mcs/class/Managed.Windows.Forms/System.Windows.Forms/Button.cs:96
  at System.Windows.Forms.ButtonBase.OnMouseUp (System.Windows.Forms.MouseEventArgs mevent) [0x000ac] in /home/cvs/mcs/class/Managed.Windows.Forms/System.Windows.Forms/ButtonBase.cs:472
  at System.Windows.Forms.Button.OnMouseUp (System.Windows.Forms.MouseEventArgs e) [0x00007] in /home/cvs/mcs/class/Managed.Windows.Forms/System.Windows.Forms/Button.cs:100
  at System.Windows.Forms.Control.WndProc (System.Windows.Forms.Message m) [0x002f1] in /home/cvs/mcs/class/Managed.Windows.Forms/System.Windows.Forms/Control.cs:3871
  at System.Windows.Forms.ButtonBase.WndProc (System.Windows.Forms.Message m) [0x0005c] in /home/cvs/mcs/class/Managed.Windows.Forms/System.Windows.Forms/ButtonBase.cs:525
  at System.Windows.Forms.Button.WndProc (System.Windows.Forms.Message m) [0x00007] in /home/cvs/mcs/class/Managed.Windows.Forms/System.Windows.Forms/Button.cs:113
  at System.Windows.Forms.Control+ControlNativeWindow.WndProc (System.Windows.Forms.Message m) [0x0000c] in /home/cvs/mcs/class/Managed.Windows.Forms/System.Windows.Forms/Control.cs:162
  at System.Windows.Forms.NativeWindow.WndProc (IntPtr hWnd, Msg msg, IntPtr wParam, IntPtr lParam) [0x0005b] in /home/cvs/mcs/class/Managed.Windows.Forms/System.Windows.Forms/NativeWindow.cs:146
  at System.Windows.Forms.XplatUIX11.DispatchMessage (System.Windows.Forms.MSG msg) [0x00022] in /home/cvs/mcs/class/Managed.Windows.Forms/System.Windows.Forms/XplatUIX11.cs:2654
  at System.Windows.Forms.XplatUI.DispatchMessage (System.Windows.Forms.MSG msg) [0x0000c] in /home/cvs/mcs/class/Managed.Windows.Forms/System.Windows.Forms/XplatUI.cs:420
  at System.Windows.Forms.Application.RunLoop (Boolean Modal, System.Windows.Forms.ApplicationContext context) [0x00244] in /home/cvs/mcs/class/Managed.Windows.Forms/System.Windows.Forms/Application.cs:490
  at System.Windows.Forms.Application.Run (System.Windows.Forms.Form mainForm) [0x0000c] in /home/cvs/mcs/class/Managed.Windows.Forms/System.Windows.Forms/Application.cs:384
  at testwin.MainForm.Main (System.String[] args) [0x0000a] in /home/cvs/winforms/filedialog/swf-filedialog.cs:32