title: .NET 4.0 Indexer with ObservableCollection
body: <p>What is the .NET C# syntax for an ObservableCollection with an indexer?  I would like an ObservableColletion and refer to the items by ordinal position or a string name.   I know you the use this to denote an indexer but I don't know how to put that in an ObservableCollection.  Thanks </p>
  
  <p>Thanks for the 4 answers.  I know how create and ObservableCollection and I know how to create an indexer.  I don't know how to combine them.  I am asking for sample code for an ObservableCollection with an ordinal and string index. 
  Thank again  </p>