C# reverse complement of a sequence : Problem is below: (need to write ReserveComplemenet method in c#)

--------------
The reverse complement of a sequence is formed by exchanging all of its nucleobases with their base complements, and then reversing the resulting sequence. The reverse complement of a DNA sequence is formed by exchanging all instances of:

A with T
T with A
G with C
C with G
and then reversing the resulting sequence.

For example, given the DNA sequence AAGCT the reverse complement is AGCTT

This method, ReverseComplement, must take the following parameter:

a reference to a DNA sequence
This method should return void and mutate the referenced DNA sequence to its reverse complement.

Im stuck and wondering how I do this? Any help would be greatly appreciated.