C# и notepad

using System;
using System.Text;
using System.Runtime.InteropServices;
 
class Program
    {
        [DllImport("user32.dll", SetLastError = true)]
        static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
        [DllImport("user32.dll")]
        static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);
       [DllImport("user32.dll")]
        static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, int len, StringBuilder st);
 
        const Int32 WM_GETTEXT = 0xD;
 
        static void Main(string[] args)
        {
            IntPtr inp = FindWindow(null,"Блокнот");
            if (inp != null)
            {
                IntPtr inedir = FindWindowEx(inp, IntPtr.Zero, "Edit", null);
                StringBuilder st = new StringBuilder(100);
                SendMessage(inedir, WM_GETTEXT, 100, st);
            }
        }
    }