title: C# System.Linq.Lookup Class Removing and Adding values
body: <p>I'm using Lookup class in C# as my prime data container for the user to select values from two  Checked List boxes.</p>
  
  <p>The Lookup class is far easier to use than using the class Dictionary>, however I cannot find methods for removing and adding values to a lookup class.</p>
  
  <p>I thought about using the where and the union, but i cant seem to get it right.</p>
  
  <p>Thanks in advance.</p>