I've created IsSubsetOf List extension based on discussion at http://stackoverflow.com/questions/332973/linq-check-whether-an-array-is-a-subset-of-another
/// <summary>
/// Determines whether a System.Collections.Generic.List<T> object is a subset of the specified collection.
/// http://stackoverflow.com/questions/332973/linq-check-whether-an-array-is-a-subset-of-another
/// </summary>
/// <param name="list"></param>
/// <param name="listToFind"></param>
/// <returns></returns>
public static bool IsSubsetOf<T>(this List<T> coll1, List<T> coll2)
{
bool isSubset = !coll1.Except(coll2).Any();
return isSubset;
}