CODEWITHSUNDEEP
c#generics
ElfsЯUs
ElfsЯUs

Reputation: 1218

How to pass a wildcard in C#

I have the following:

public class Foo<T> : Goo
    where T: SomeClass<?>, new()

I know that ? is not a real wildcard in C#, however, how would you write this correctly in C# such that SomeClass can take any class as an argument? I tried using object, but then I get an error "...there is no implicit reference conversion from..."

Thanks!

Upvotes: 5

Views: 276

Answers (1)

Alexei Levenkov
Alexei Levenkov

Reputation: 100547

You have to specify second type argument (i.e. Y in my sample), note that Y could be anything as there are no restrictions, even the same as T. 

public class Foo<T, Y> : Goo
    where T: SomeClass<Y>, new()

Another option is to specify only second class if you only need to use SomeClass<Y> in your generic class, you will not need new() restriction because compiler knows in advance that SomeClass<T> have default constructor:

public class Foo<Y> : Goo{
  public SomeClass<Y> Value;

  public void Setup() { Value = new SomeClass<Y>(); }
}

Upvotes: 6

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