It is now possible to extend or change the provided API version format, but that capability comes with several rules:

1. You must extend ApiVersion
2. You must override:
   • GetHashCode
   • CompareTo
   • ToString(string,IFormatProvider)
3. You must implement IApiVersionParser
   • It may be possible to extend ApiVersionParser depending on your requirements

You will likely need to extend ApiVersionFormatProvider or implement a custom IFormatProvider. Although not strictly required, you may want to implement operator overloads for your custom type to retain functional parity with ApiVersion. The custom parser will need to be passed to components that accept IApiVersionParser and/or replace the default implementation registered for dependency injection.

You should consider the impact that a custom API version may have on clients. Your custom format and parsing logic may need to be distributed to them for to use.