title: C# search text file, return all lines containing a word
body: <p>I need help with a program i'm building at my internship.
  The idea is to check how frequent a user logs in on any PC.
  When a user logs in, that information is logged in a text file, like this format.</p>
  
  <pre><code>01-01-2011 16:47:10-002481C218B0-WS3092-Chsbe (XP-D790PRO1)
  </code></pre>
  
  <p>Now i need to search the text file and (for example) search the text file for all login dates for the user Chsbe.</p>
  
  <p>My code so far:</p>
  
  <pre><code>private void btnZoek_Click(object sender, EventArgs e)
          {
              int counter = 0; string line;  
              // Read the file and display it line by line. 
              System.IO.StreamReader file = new System.IO.StreamReader("c:\\log.txt"); 
              while((line = file.ReadLine()) != null)
              {     if ( line.Contains(txtZoek.Text) )     
              {
                  txtResult.Text = line.ToString();                
              }     
  
              }  
              file.Close(); 
          } 
  </code></pre>
  
  <p>My question is, How do i return all the strings in the log containing the searchterm to txtResult?</p>