/// <summary>
/// Retains only the elements in this set that are contained in the specified collection.
/// </summary>
/// <param name="c">Collection that defines the set of elements to be retained.</param>
/// <returns><c>true</c> if this set changed as a result of this operation.</returns>
public sealed override bool RetainAll(ICollection c)
{
//Put data from C into a set so we can use the Contains() method.
Set cSet = new HybridSet(c);
//We are going to build a set of elements to remove.
Set removeSet = new HybridSet();
foreach(object o in this)
{
//If C does not contain O, then we need to remove O from our
//set. We can't do this while iterating through our set, so
//we put it into RemoveSet for later.
if(!cSet.Contains(o))
removeSet.Add(o);
}
return this.RemoveAll(removeSet);
}
