using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.IO;
using System.Runtime.InteropServices;
namespace WfpApp
{
 class PositionNotepad
 {
 [DllImport("User32.dll", EntryPoint = "FindWindow")]
 private 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 bool SetForegroundWindow(IntPtr hWnd);
 ///<summary>  
 /// 定位到txt文件指定行  
 ///</summary>  
 ///<param name="strFullName">文件路徑</param>  
 ///<param name="strRow">指定行</param>  
 ///<returns>定位是否成功</returns>  
 public static bool PositionNotePad(string strFullName, string strRow)
 {
  int iRow;
  int.TryParse(strRow, out iRow);
  if (iRow <= 0)
  {
  return false;
  }
  //查看當前文件是否已打開 
  IntPtr hwnd = FindWindow("Notepad", string.Format("{0} - 記事本", Path.GetFileName(strFullName)));
  if (hwnd.ToInt32() == 0)
  {
  Process p = Process.Start(@"notepad.exe", strFullName);
  //等一秒，等文本打開，焦點去到notepad
  p.WaitForInputIdle(1000);
  System.Windows.Forms.SendKeys.SendWait("{DOWN " + (iRow - 1) + "}");
  System.Windows.Forms.SendKeys.SendWait("{HOME}"); //行首
  System.Windows.Forms.SendKeys.SendWait("+{END}"); //選中當前行
  return true;
  }
  else
  {
  hwnd = FindWindowEx(hwnd, IntPtr.Zero, "Edit", string.Empty);
  if (hwnd.ToInt32() == 0)
   return false;
  else
  {
   SetForegroundWindow(hwnd);
   System.Windows.Forms.SendKeys.SendWait("^{HOME}");//將光標定位到首行
   System.Windows.Forms.SendKeys.SendWait("{DOWN " + (iRow - 1) + "}");
   System.Windows.Forms.SendKeys.SendWait("{HOME}"); //行首
   System.Windows.Forms.SendKeys.SendWait("+{END}"); //選中當前行
  }
  }
  return true;
 }
 }
}

string path = @"C:\Users\ZKK\Desktop\English.txt";
bool res = PositionNotepad.PositionNotePad(path, "5");