Question: I am working on CRC64 Reversing algorithm on C# but unable to code it. If anyone can help me out, it will be nice of him. I am desperate to complete the coding.

Answer: 
That's not possible. CRC is a [hash function](http://en.wikipedia.org/wiki/Hash_function). Hash functions **cannot** be reversed. The best you can do is try and find collisions for a given hash, but they are *designed* to be hard to find such collisions..
Pretty sure he's asking for a 'reflected' algorithm.
The 'standard' and 'reflected' algorithms are an exact mirror
image of each other, including the polynomial used in each.
A message created/checked on one-endian system should not be
reversed on other-endian system as this can harm the checks
ability to identify burst errors. An 'mirror' algorithm on
the other-endian system will produce a check that exactly
matches the transmitted check value. Not sure if this code
is still needed? I could probably do it for you with the
original code to be reflected.