[C#] ช่วยหน่อยครับ หานานแล้วไม่เจอทำโปรเจคส่งครับต้องการมากๆครับ

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.IO;

namespace PROJECT
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string path = @"D:\\Soft Dev\\PROJECT\\TEST TEXT\\text4.txt";

            if (!File.Exists(path))
            {
                string createText ="";
                File.WriteAllText(path, createText);
            }

            string appendText = textBox1.Text + Environment.NewLine;
            File.AppendAllText(path, appendText);

            string readText = File.ReadAllText(path);
            Console.WriteLine(readText);
        }

        private void button2_Click(object sender, EventArgs e)
        {
            string strline = null;
            string[] strtext = null;
            int count = 0;

            FileStream FileInput = new FileStream("D:\\Soft Dev\\PROJECT\\TEST TEXT\\text4.txt", FileMode.Open);
            StreamReader sr = new StreamReader(FileInput);

            while (sr.Peek() != -1)
            {
                strline = sr.ReadLine();
                strtext[count] += strline;
                count++;
            }
            for (int i = 0; i < count; i++)
            {
                textBox1.Text += strtext[i];
            }
            sr.Close();
            FileInput.Close();
        }

    }
}