private void Form1_Load(object sender, EventArgs e) { NativeMethods.CHANGEFILTERSTRUCT changeFilter = new NativeMethods.CHANGEFILTERSTRUCT(); changeFilter.size = (uint)Marshal.SizeOf(changeFilter); changeFilter.info = 0; if (!NativeMethods.ChangeWindowMessageFilterEx(this.Handle, NativeMethods.WM_COPYDATA, NativeMethods.ChangeWindowMessageFilterExAction.Allow, ref changeFilter)) { int error = Marshal.GetLastWin32Error(); MessageBox.Show(String.Format("The error {0} occured.", error)); } }