Restrict type of generic class to List of struct

Question

A generic interface is available that looks like this

interface IMatch<T>
{
    bool MatchWithExpected(T actualValue);
}

Implementations of this interface for different types is available already (Int, struct, Enum etc.,).

I have a struct called ObjectType . I want an implementation of the above interface that works with a list of ObjectType .

The only way I was able to do this is by doing the following

class MultiStructMatch<T> : IMatch<T> where T is List<ObjectType> 

Is there any way to make List<ObjectType> generic that denotes List<struct> ? I tried List<System.ValueType> but cannot convert List<ObjectType> to List<System.ValueType> .

Answer 1

You could pass List<T> to IMatch<> and apply the type constraint to T:

class MultiStructMatch<T> : IMatch<List<T>> where T: struct
{
}

and instantiate this with:

struct M
{
}
...
var m = new MultiStructMatch<M>;

Answer 2

You'll need a second generic parameter and declare your class like this:

class MultiStructMatch<T, TElement> : IMatch<T> 
    where T : List<TElement> 
    where TElement : struct
{}

And instantiate it eg:

var m = new MultiStructMatch<List<ObjectType>, ObjectType>();

This syntax is a little clumsy, because the extra type parameter seems redundant. But I don't see a better way to apply the struct constraint.

Obviously Panagiotis found the better syntax.