c#中檔案操作

   //DirectoryInfo dir = new DirectoryInfo("c:\\");
          //  System.IO .FileSystemInfo[] fis = dir.GetFileSystemInfos();
          //  if (fis[1] is DirectoryInfo )
          //  {
          //      //fis[1]是一個檔案夾
          //  }
          //  if (fis[1] is FileInfo)
          //  {
          //      //fis[1]是一個檔案
          //  }
        private void operatorFileBtn_Click(object sender, EventArgs e)
        {
            FileInfo fi = new FileInfo("aa.txt");
            if (fi.Exists)
            {
                //向檔案中追加資訊
                using (StreamWriter sw =fi.AppendText ())
                {
                    sw.Write("這是測試資訊:::");
                }
            }
            else
            {
                //建立檔案並寫入資訊
                using (StreamWriter sw = fi.CreateText())
                {
                    sw.Write("建立檔案::");
                }
            }
           
        }

        private void readBtn_Click(object sender, EventArgs e)
        {
            FileInfo fi = new FileInfo("aa.txt");
            if (fi.Exists)
            {
                //讀取檔案內容
                using (StreamReader sr=fi.OpenText())
                {
                    this.richTextBox1.Text = sr.ReadToEnd();
                }
            }
            fi.CopyTo("d:aa.txt");
            fi.Create();
            fi.Delete();
        }