读TXT：

txtpath = System.AppDomain.CurrentDomain.BaseDirectory.ToString() + "test.txt";if (File.Exists(txtpath)){　　StreamReader sr = new StreamReader(txtpath, Encoding.UTF8);　　String line;　　while ((line = sr.ReadLine()) != null)　　{　　　　this.textBox3.Text = line;　　}　　sr.Close();}

写TXT：

txtpath = System.AppDomain.CurrentDomain.BaseDirectory.ToString() + "test.txt";if (File.Exists(txtpath)){    FileStream stream2 = File.Open(txtpath, FileMode.OpenOrCreate, FileAccess.Write);    stream2.Seek(0, SeekOrigin.Begin);    stream2.SetLength(0); //清空txt文件    StreamWriter sw = new StreamWriter(stream2);    sw.Write(this.textBox4.Text.ToString());    sw.Flush();    sw.Close();    stream2.Close();}else{    FileStream fs = new FileStream(txtpath, FileMode.CreateNew);    StreamWriter sw = new StreamWriter(fs);    sw.Write(this.textBox4.Text.ToString());    sw.Flush();    sw.Close();    fs.Close();}