C# implements the method of writing text file contents

private void write_txt(string str1, string str2, string str3)
{
   currentTime = ;
  string strYMD = ("d");
  string FILE_NAME = "MyFileSend" + strYMD + ".txt";
  // Create a different file name according to date every day  StreamWriter sr;
  if ((FILE_NAME))
  //If the file exists, create an object  {
  sr = (FILE_NAME);
  }
  else
  //If the file does not exist, create an object  {
  sr = (FILE_NAME);
  }
  (str1 + "　" + str2 + "　" + ("yyyy-mm-dd hh:mm:ss") + " " + str3 + "\r\n");
  //Write the passed string plus time to a line of text file  ();
}