为啥我的postmessage 到记事本的按键信息无效， 哪位大大帮我分析一下？

已经注意子窗口的问题了， 对比spy++的句柄，没有找错edit控件窗口， 但无法写进去 。 看了msdn，也将焦点重置加入，还是无法写入，不知是什么原因？



using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;


namespace SendKeyInfo
{
    class SendController
    {

        // 导入窗口名称列表

        const string titleW = "notepad";

         

        private const int WM_KEYDOWN = 0x0100;
        private const int WM_KEYUP = 0x0101;
        private const int WM_SETFOCUS = 0x0007;
        private const int WM_LOSTFOCUS = 0x0008;
        private const int WM_CHAR = 0x0102; 

        private const int VK_S = 83;

        int p_hWnd, hProcess, delay, PID,child;

        public bool sclick()
        {
            p_hWnd = SendUtil.FindWindowExA(0, 0, titleW, null);

            if (p_hWnd == 0)
            {
                MessageBox.Show("请先启动!");
                return false;
            }
            else
            {

                child = SendUtil.FindWindowExA(p_hWnd,0,"edit" ,null);
                MessageBox.Show(child+"");
                SendUtil.GetWindowThreadProcessId(child, out PID);
                SendUtil.PostMessageA(PID, WM_LOSTFOCUS, 0, 0);
                
                SendUtil.PostMessageA(PID, WM_SETFOCUS, 0, 0);
                SendUtil.SendMessageA(PID, WM_KEYDOWN, VK_S, 0);
                SendUtil.PostMessageA(PID, WM_CHAR, '1', 0);
                MessageBox.Show("....");
                return true;
            }
        }
    }
}
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补充：.NET技术 ,  C#