Generic constraint to match numeric types [duplicate]

Question

I'm trying to write an extension method on numeric types to be used in a fluent testing framework I'm building. Basically, I want to do this:

public static ShouldBeGreaterThan<T>(this T actual, T expected, string message)     where T : int || T: double || etc... 

Just where T : struct doesn't do, since that will also match string and bool, and possibly something else I'm forgetting. is there something I can do to match only numeric types? (Specifically types that implement the > and < operators, so I can compare them... If this means I'm matching dates as well, it doesn't really matter - the extension will still do what I expect.)

Answer 1

In this case you want to constrain your generic to the IComparable interface, which gives you access to the CompareTo method, since this interface allows you to answer the question ShouldBeGreaterThan.

Numeric types will implement that interface and the fact that it also works on strings shouldn't bother you that much.

Answer 2

where T : struct,            IComparable,            IComparable<T>,            IConvertible,            IEquatable<T>,            IFormattable 

That's the closest I can get to a numeric constraint. All the numeric types implement these 5 interfaces, but IFormattable is not implemented by bool, and strings are a reference type, so they're not applicable.

There's some other things that implement these - DateTime for example, so it's not really as required, but prevents a lot of instantiations you don't want.