/// <summary>
/// Add an index to this IQueryCache.
/// </summary>
/// <remarks>
/// This allows to correlate values stored in this
/// <i>indexed cache</i> (or attributes of those values) to the
/// corresponding keys in the indexed cache and increase the
/// performance of <b>GetKeys</b> and <b>GetEntries</b> methods.
/// </remarks>
/// <param name="extractor">
/// The <see cref="IValueExtractor"/> object that is used to extract
/// an indexable object from a value stored in the indexed
/// cache. Must not be <c>null</c>.
/// </param>
/// <param name="isOrdered">
/// <b>true</b> if the contents of the indexed information should be
/// ordered; <b>false</b> otherwise.
/// </param>
/// <param name="comparer">
/// The <b>IComparer</b> object which imposes an ordering on entries
/// in the indexed cache; or <c>null</c> if the entries' values
/// natural ordering should be used.
/// </param>
public virtual void AddIndex(IValueExtractor extractor, bool isOrdered, IComparer comparer)
{
NamedCache.AddIndex(extractor, isOrdered, comparer);
}