Is it possible to pass an enum as a type parameter for an interface, or is there a way I can achieve the same thing a different way?
E.g.
public interface IServiceResponse<R, enumServiceID> {}
Thanks in advance.
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Duplicate of this, which is already one of any duplicates of this.ForeverZer0– ForeverZer02018-07-15 01:11:23 +00:00Commented Jul 15, 2018 at 1:11
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Possible duplicate of Anyone know a good workaround for the lack of an enum generic constraint?ForeverZer0– ForeverZer02018-07-15 01:12:11 +00:00Commented Jul 15, 2018 at 1:12
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1 Answer
You're declaring the interface so the Type Parameters are symbolic representations of a type, not an actual concrete type. You can put a type parameter that you expect to be an enum type (say TEnum), and then constrain it to be a Value Type (where TEnum : struct), but, unfortunately you can't constrain it to be an enum. Once you do that, you can declare a class the implements that interface with a concrete enum type:
public class MyServiceResponse : IServiceResponse<MyRType, EnumServiceId> { }
UPDATE
As noted by @BJMeyers in the comments, C# now supports Enum constraints on type parameters. As a result, you can do something like this now:
public class MyServiceResponse : IServiceResponse<MyRType, TEnumService> where TEnumService : struct, System.Enum
{
public TEnumService EnumServiceId { get; set; }
// ... more code here ...
}
I'm not sure if that's what you want, but if it is, you can do it. Note, the struct in the where constraint is important (remember that System.Enum is a class, not a struct).
3 Comments
BJ Myers
Noteworthy: C# 7.3 supports the
where T : Enum constraint.
Flydog57
Alleluia. I've silently asked for that so many times over the years. Thanks for letting me know!
ForeverZer0
@BJMyers Finally, glad to have learned that, been long overdue. Now all we need is "numeric" type constraints...