covariance

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Covariance and contravariance for wildcarded types

Can you please explain why it is possible to do: import java.util.ArrayList; import java.util.List; public class Covariance {[详细]

2023-03-08 07:11 分类：问答
Inheritance & Lists

Class B extends class A. I have a list of B (List<B> list1), but for some operations I need only class A fields, but List<A> list2 = list1 doesn\'t work. H开发者_如何学Cow can this problem[详细]

2023-03-07 08:18 分类：问答
Why doesn't this generic extension method compile?

The code is a little weird, so bear with me (keep in mind this scenario did come up in production code).[详细]

2023-03-06 08:37 分类：问答
Question about generics in C# comparing to Java

In Java I can specify generic with wildcard \"?\". It is possible to create a map like this one: Map<String, ?>.[详细]

2023-03-05 16:29 分类：问答
Invalid Types in VB.NET

I have a function which returns a list of products and a page which displays then, but when I try to load the list on the page, I get a cryptic error:[详细]

2023-03-04 13:45 分类：问答
Type extraction in Scala

I am pretty new to Scala and advanced programming languages. I try to solve the following problem. I have got:[详细]

2023-03-03 19:55 分类：问答
Why can't I cast from a List<MyClass> to List<object>?

I have a List of objects, which are of my type QuoteHeader and I want to pass this list as a list of objects to a method which is able to accept a List<object>.[详细]

2023-03-02 22:39 分类：问答
c++: exact type of contained objects without casts

I got the classic Shape hierarchy example... struct Shape { // abstract type Shape (int x, int y); int x;[详细]

2023-03-02 20:01 分类：问答
Referencing a derived type inside itself

I have something link this: public abstract class Wrapper<T, TWrapped>: where TWrapped : Wrapper<T, TWrapped>[详细]

2023-03-02 13:05 分类：问答
Covariance and IList

I would like a Covariant collection whose items can be retrieved by index.IEnumerable is the only .net collection that I\'m aware of that is Covariant, but it does not have this index support.[详细]

2023-03-02 03:09 分类：问答