title: How to use File.WriteAllText but don't overwrite the old text?
body: <p>i want to return all data to txt file from my csv</p>
  
  <pre><code>string fileName = "../../TechFiles/";
  List&lt;string&gt; listA = new List&lt;string&gt;();
  
  using (var reader = new StreamReader(ConfigurationManager.AppSettings["ConfigurationSource"]))
  {
      var hdr2 = "2012-05-09 12:52:00";
      var hdr1 = "Account";
  
      while (!reader.EndOfStream)
      {
          var line = reader.ReadLine();
          var values = line.Split(',');
  
  
          listA.Add(values[0]);
      csv = new StringBuilder();
  newLine = string.Format("HDR {0} {1}\r\n{2}{3}" , hdr1,line, Environment.NewLine);
          csv.Append(newLine);
  
          File.WriteAllText(String.Format("{0}{1}", fileName, values[4] + ".txt"), csv.ToString());
      }
  }
  </code></pre>