title: Index out of range exception in custom generic collection
body: <p>I wrote a class which imports System.Collections.ObjectModel. For the management of the collection, I've written:</p>
  
  <pre><code>Default Public ReadOnly Property Item(ByVal vntIndexKey As Integer) As ItemType
      Get
          Return CType(mCol.Item(vntIndexKey), ItemType)
      End Get
  End Property
  </code></pre>
  
  <p>Then when i was debugging, I was told: </p>
  
  <p>"Index was out of range. Must be non-negative and less than the size of the collection."</p>
  
  <p>The "ItemType" is always being an object, and during the debug, I can see that vntIndexKey=1.</p>
  
  <p>Could someone tell me why?</p>