title: if ListBox Contains, don't add
body: <p>I've got a Method:</p>
  
  <pre><code>FillListBox();
  </code></pre>
  
  <p>I call this method from different places.. But sometimes it happens, that things were loaded twice!</p>
  
  <p>Now I'm trying to do something like:</p>
  
  <pre><code>if (listBox.Items[1].ToString() == "hello")
  {
     DO NOT FILL
  }
  else
  {
     FILL
  }
  </code></pre>
  
  <p>THIS DONT WORKS! :( </p>
  
  <pre><code>Fault: InvalidArgument=Value of '1' is not valid for 'index'.
  Parameter name: index
  </code></pre>
  
  <p>And something like that:</p>
  
  <pre><code>if(listBox.Items.Contains("hello"))
  {
     DONT FILL
  }
  </code></pre>
  
  <p>Dont works too :(</p>
  
  <p>What can I do?</p>