Question

Aloha

I have a method with (pseudo) signature:

public static T Parse<T>(string datadictionary) where T : List<U> 

This doesn’t build. How can I restrict the in the method to accept only generic List<> objects (which should of cource not contain T’s but something else 🙂

I need to restrict the type of T because I need to call a method on it in this code. The type passed in is a custom collection (based on List).

public class MyCollection<T> : List<T> where T: MyClass, new() {     public void Foo(); }   public static T Parse<T>(string datadictionary) where T : MyCollection<U> {     T.Foo(); } 

-Edoode

Answer 1

Well, you can have two type parameters:

public static T Parse<T, U>(string datadictionary) where T : List<U> 

That way you’ll also actually know what U is (in a compile-time manner)…

EDIT: Alternatively (and better), just specify the element type and change the return type:

public static List<T> Parse<T>(string datadictionary) 

e.g.

List<int> data = Parse<int>(whatever); 

Note that you may wish to change from List<T> to IList<T> or even a broader interface.