HashAlgorithm.Create Method (String)

Regarding the issue @PTaylor noted, it is possible to register any number of hashing algorithms with the .NET cryptographic system. The following page on the cryptographicSettings element that can be added to machine.config explains exactly how:

http://msdn.microsoft.com/en-us/library/hwayhcwf(VS.71).aspx

In a nutshell, you can register cryptoNameMappings that define hashing algorithm types, nameEntries that define user friendly names for hashing algorithms, and oidMap entries that associate OID's with registered class names. You should then be able to use the HashingAlgorithm.Create(string) method to create any kind of algorithm...built into .NET or even custom algorithms you may write yourself. You can then feel safe and free to configure an algorithm name and not worry it won't work with a new version of .NET.

In order to future-proof an application, it's necessary to assume that hash algorithms will be phased out and new ones phased in. I expect, for example, that new framework versions released after SHA-3 is approved will include an implementation thereof. If I want to write future-proof code which reads the name of the algorithm to use from a config file, I need to handle the name not being recognised (if someone runs a version with a config file for .Net 6 on a machine with .Net 4, for instance).

My tests indicate that this method returns null if the algorithm name is unrecognised. Can I assume that if the name is invalid this method will always return null?