文件读写操作

如图，点击选择文件则读取文件路径，读取时将文件内容显示到文本框中，写入时将文本框内容写入文件

namespace 文件操作
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        /// <summary>
/// 选择文件
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
        private void button1_Click(object sender, EventArgs e)
        {
            OpenFileDialog open =new OpenFileDialog();
            open.Filter ="*.txt|*.txt";                //文件类型
if (open.ShowDialog() == DialogResult.OK)
            {
                textBox1.Text = open.FileName;
            }
        }
        /// <summary>
/// 读取文件
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
        private void button2_Click(object sender, EventArgs e)
        {
            if (textBox1.Text.Length <0)
            {
                return;
            }
            Stream stream =new FileStream(textBox1.Text, FileMode.Open, FileAccess.Read);
            using (StreamReader reader =new StreamReader(stream, Encoding.Default))
            {
                string pp ="";
                while (reader.Peek() >-1)
                {
                    pp += reader.ReadLine();
                }
                richTextBox1.Text = pp;

            }
        }
        /// <summary>
/// 写入文件
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
        private void button3_Click(object sender, EventArgs e)
        {
            Stream stream =new FileStream(textBox1.Text, FileMode.Create, FileAccess.Write);
            StreamWriter writer =new StreamWriter(stream, Encoding.Default);
            writer.WriteLine(richTextBox1.Text);

        }
    }
}