Вставка текста и нажатие на кнопку в чужом приложении

using System;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Diagnostics;
 
namespace WindowsFormsOPEN
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        [DllImport("User32.dll")]
        static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
        [DllImport("User32.dll")]
        static extern int SetForegroundWindow(IntPtr hWnd);
        private void button1_Click(object sender, EventArgs e)
        {
            Process process = System.Diagnostics.Process.Start(@"C:\Program Files (x86)\Etxt Antiplagiat\EtxtAntiplagiat.exe");
            process.WaitForInputIdle();
            IntPtr hWndNotepad = FindWindow(null, "AntiPlagiarium.NET");
            SetForegroundWindow(hWndNotepad);
                SendKeys.SendWait("Hello!!!");
        }
    }
}

 
 const string user32 = "user32.dll";
 
public delegate bool EnumWindowsProc(IntPtr hWnd, IntPtr lParam);
 
[DllImport(user32)]
        static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
 
[DllImport(user32, SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    static extern bool EnumChildWindows(IntPtr hWndParent, EnumWindowsProc lpEnumFunc, IntPtr lParam);
 
    [DllImport(user32, SetLastError = true)]
    static extern int GetWindowText(IntPtr hWnd, StringBuilder lpString, int nMaxCount);
 
    [DllImport(user32, SetLastError = true)]
    static extern int GetClassName(IntPtr hWnd, StringBuilder lpString, int nMaxCount);
 
    [DllImport(user32, SetLastError = true)]
    static extern int GetWindowTextLength(IntPtr hWnd);
 
  [DllImport(user32, SetLastError = true)]
    static extern IntPtr GetParent(IntPtr hWnd);
 
public struct window
{
    public string windowname;
    public string classname;
}
 
 string GetWindowText(IntPtr hWnd)
    {
        int len = GetWindowTextLength(hWnd) + 1;
        StringBuilder sb = new StringBuilder(len);
        len = GetWindowText(hWnd, sb, len);
 
        return sb.ToString(0, len);
    }
    string GetWindowClass(IntPtr hWnd)
    {
        int len = 260; 
        StringBuilder sb = new StringBuilder(len);
        len = GetClassName(hWnd, sb, len);
        return sb.ToString(0, len);
    }

public List<window> GetChildControls(IntPtr parent)
    {
         List<window> wnds = new List<window>();
        EnumChildWindows(parent, new EnumWindowsProc((hWnd1, lParam2) =>
            {
                if (GetParent(hWnd1) != parent)
                    return false;
                
                window win = new window();
                win.windowname = GetWindowText(hWnd1);
                win.classname = GetWindowClass(hWnd1);
                wnds.Add(win);
                return true;
            }), IntPtr.Zero);     
          return wnds;
    }
 
IntPtr hWndNotepad = FindWindow(null, "AntiPlagiarium.NET");
List<window> aa= GetChildControls(hWndNotepad);