// Create a new instance of Crc using the algorithm of your choice
var crc = CrcAlgorithm.CreateCrc16CcittFalse();

// Give it some bytes to chew on - you can call this multiple times if needed
crc.Append(Encoding.ASCII.GetBytes("Hurray for cake!"));

// Get the output - as a hex string, byte array or unsigned integer
Console.WriteLine(crc.ToHexString());

CRC is an interesting standard. It's an interesting standard, because it isn't really a standard at all. It seems rather better to be considered an idea. Many people have taken that core idea of CRC and implemented it in many different ways. At the time of writing Wikipedia lists 61 different implementations. There are even tools available that support over 100 implementations.

Each of these implementations (or algorithms, as they're more commonly known) differ in the following ways:

• They vary in the width, or the size of the outputted hash.
• The use different underlying polynomials.
• The algorithms are seeded with differing initial values.
• Some reflect the input before processing it
• Some reflect the output before returning it
• Some apply a XOR to the output return it

(This is taken straight from the fantastic work of Ross N. Williams and I take no credit.)

InvertedTomato.Crc takes into account all of these parameters allowing it to be customised to the particular algorithm you need.

InvertedTomato.Crc allows you to plug any parameters you'd like into the constructor to support any algorithm you'd like (so long as it's width is 8-64bits), however I've included some of the most common algorithms for convenience borrowed from Meetantony.

If you're keen to know more about CRC, I can't over-recommend Ross N. Williams's 'A Painless Guide ot CRC Error Detection Algorithms. I haven't been able to find the original URL of it though, so I've mirrored it here.

You can find it on NuGet.