#1,146 – Generics Don’t Support Covariance

In C#, arrays are covariant, so you can do the following:

            // Array covariance--OK
            Dog[] dogs = new Terrier[5];

Generics in C#, however, are not covariant (they are invariant). The following code will not compile.

            // Generic covariance--not OK (compiler error)
            List<Dog> moreDogs = new List<Terrier>();

About Sean
Software developer in the Twin Cities area, passionate about .NET technologies. Equally passionate about my own personal projects related to family history and preservation of family stories and photos.

6 Responses to #1,146 – Generics Don’t Support Covariance

  1. Pingback: Dew Drop – July 25, 2014 (#1822) | Morning Dew

  2. Joseph says:

    Actually, not true. Generics in C# can be both covariant and contravariant. See http://msdn.microsoft.com/en-us/library/dd799517.aspx.

  3. Joseph says:

    To clarify, List is invariant, but that’s because the type must go both directions. In a read only collection or IEnumerable or Action or Func, the generic type may be covariant or contravariant.

  4. vikram says:

    class cls

    list lstcls = new list();
    cls[] arrcls = new cls[10];

    what is the diff of list class and array class?

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