Methods for content uniqueness calculation on C#

I have a set of text files. I want to calculate a content uniqueness for different subsets.

E.g. we have 10 documents (A1 - A10) and want to calculate the uniqueness for subset of documents A1 and A2. So the result must be some value from 0 to开发者_JAVA百科 1 (1 - absolutely unique content, 0 - absolutely duplicated content).

What methods for content uniqueness calculation do you know? Please suggest these methods with .NET implementations.

Thanks.

You can use the FileStream Class.

Here's a nice implementation:
http://www.java2s.com/Code/CSharp/File-Stream/Comparetwofiles.htm