Filestream读取或写入文件

using System.IO;//引用 System.IO
namespace filestream
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void btnWrite_Click(object sender, EventArgs e)
        {
            SaveFileDialog sfd = new SaveFileDialog();

            sfd.Filter = "文本文件|*.txt|c#文件|*.cs";

            if (sfd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
            {
                txtPath.Text = sfd.FileName;//保存的路径
                using (FileStream fs = new FileStream(txtPath.Text, FileMode.Create))
                {
                    string txt = txtContent.Text;
                    byte[] buffer = Encoding.UTF8.GetBytes(txt);
                    fs.Write(buffer, 0, buffer.Length);
                }
            }
        }

        private void btnRead_Click(object sender, EventArgs e)
        {
            OpenFileDialog ofd = new OpenFileDialog();
            ofd.Filter = "文本文件|*.txt";
            if (ofd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
            { 
                txtPath.Text  = ofd.FileName;
                using (FileStream fs = new FileStream(txtPath.Text, FileMode.Open))
                { 
                    //byte[] buffer = new byte[fs.Length];
                    //fs.Read(buffer, 0, buffer.Length);

                    //string msg = Encoding.UTF8.GetString(buffer);
                    //txtContent.Text = msg;


                    using (StreamReader sr = new StreamReader(fs,Encoding.UTF8))
                    {
                        string msg = sr.ReadToEnd();
                        txtContent.Text = msg;
                    }
                }
            }
        }
    }
}