I have a class Card, which has property Rank (1,2,3 etc) and I have a list of Cards and I wish to find all the Cards with the same Rank value in that list.

The list of Cards is sorted by Rank beforehand.

What would be the fasted way in .NET (using LINQ, if possible) to find all the objects with the same property value. 

I don't know what the property value is beforehand, so I have to go through and compare. Until now I've been looping and keeping references to previous objects to compare, but I was wondering if there is not some easier way to do this?

Point is I need to be able to find N elements in a list with the same property value. 

There might not be, but I thought I'd still ask.