title: How to add new line into txt file
body: <p>I'd like to add new line with text to my date.txt file, but instead of adding it into existing date.txt, app is creating new date.txt file..</p>
  
  <pre><code>TextWriter tw = new StreamWriter("date.txt");
  
  // write a line of text to the file
  tw.WriteLine(DateTime.Now);
  
  // close the stream
  tw.Close();
  </code></pre>
  
  <p>I'd like to open txt file, add some text, close it, and later after clicking something: open date.txt, add text, and close it again.</p>
  
  <p>So i can get: </p>
  
  <p>Button pressed: txt opened -> added current time, then close it. Another button pressed, txt opened -> added text "OK", or "NOT OK" in the same line, then close it again.</p>
  
  <p>So my txt file will look like that:</p>
  
  <pre><code>2011-11-24 10:00:00 OK
  2011-11-25 11:00:00 NOT OK
  </code></pre>
  
  <p>How can i do this? Thanks!</p>