C# Sendmessage问题

Question

网上找的，将内容写到记事本中，  [DllImport("user32.dll", EntryPoint = "FindWindowEx")]
        public static extern IntPtr FindWindowEx(IntPtr hWnd1, int hWnd2, string lpsz1, string lpsz2);
        [DllImport("user32.dll", EntryPoint = "GetWindowText")]
        public static extern IntPtr GetWindowText(IntPtr hwnd, StringBuilder lpString, int cch);
        [DllImport("User32 ")]
        public static extern bool SendMessage(IntPtr hWnd, int Msg, int wParam, IntPtr lParam);
        [DllImport("User32 ")]
        public static extern bool SendMessage(IntPtr hWnd, int Msg, int wParam, string lParam);
        public const int WM_GETTEXT = 0xD;
        public const int WM_SETTEXT = 0xC;
        private void button11_Click(object sender, EventArgs e)
        {
            
            Process p1 = Process.Start("Notepad.exe");
            p1.WaitForInputIdle();            
            Process[] process_array = Process.GetProcesses();
            IntPtr hNotepad = IntPtr.Zero;            
            foreach (Process p in process_array)
            {
                if (p.MainWindowTitle.IndexOf("记事本") != -1)//找到了
                {
                    hNotepad = p.MainWindowHandle;
                    break;
                }
            }
            if (hNotepad != IntPtr.Zero)
            {
                
                IntPtr hEdit = FindWindowEx(hNotepad, 0, "Edit", ""); 
               
                SendMessage(hEdit, WM_SETTEXT, 100, "这里是测试文本");                
                string w = " ";
                IntPtr ptr = Marshal.StringToHGlobalAnsi(w);
                if (SendMessage(hEdit, WM_GETTEXT, 100, ptr)) Console.WriteLine(Marshal.PtrToStringAnsi(ptr));
            }        }