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.)
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.
Edit:
My comment from 2020 is not true anymore!
Since .NET 7 you could also consider constraining to the INumber<TSelf>
- incidentally, the interface inherits from IComparable
but would then indeed exclude e.g. the string
type. Additionally, though, the interface also inherits from the IComparisonOperators
interface, which will give you all the operators you'd expect (<, <=, >=, >, ==, !=
)