title: Avoid duplicate values in Collection
body: <p>I have following values, and I want to add these to a collection. If the values are already in the collection, a message should show "this is already added in your collection".</p>
  
  <pre><code>Dim OrdLines As New Collection
  
  OrdLines.Add (111,this is first item)
  
  OrdLines.Add (222,this is second item)
  
  OrdLines.Add (333,this is third item)
  
  OrdLines.Add (444,this is fourth item)
  </code></pre>
  
  <p>How do I avoid duplicate values in a collection?</p>