There is probably another method I could add too: TryGetValue(string property, out IValues result)
This being non-generic allows simple access to any type of value on the property.

Actually, I'm just going to add that now to this PR.

Seems reasonable. Is there a specific reason you need this feature? I can't think of any obvious use cases.

The primary motivation for me is that it makes it easier to create Schema objects at runtime - especially when the properties are provided from unreliable 3rd party data (for example, parsing Microdata from HTML into Schema objects).

Besides these methods, there are a couple of other changes I'd like to make for other methods of reading/writing/converting schema objects easier too. For example, moving some of the string-conversion logic in ValuesJsonConverter to a separate class that can be access directly (again, useful for things like converting Microdata).

... there are a couple of other changes I'd like to make for other methods ...

I should clarify with this - I was originally going to include some of that in this PR but some of the changes would overlap with the changes for System.Text.Json support and would make merging a bit of a pain.