Reduction of generic types <T>

Question

There is a task:

public class A { } public class A1 : A { } public class A2 : A { } public class B<T> where T : A { } public class B1 : B<A1> { } public class B2 : B<A2> { } public class Conteiner<T, U> where T : B<U> where U : A { T[] list; public T this[int index] { get { return list[index]; } set { list[index] = value; } } public void Set<K, N, M>(K conteiner) where K : Conteiner<N, M> where N : B<M> where M : A { list[0] = conteiner[0]; <------Ошибка не удается преобразовать тип N в T. } }

How to solve or work around a problem?

Override Set : public void Set(Conteiner<T, U> conteiner) .
Otherwise, it is simply impossible, since you can have U=A1 , and M=A2 and these types are not given
Possible duplicate question: What is the essence of the covariance and contravariance of delegates?
What is the point of doing Conteiner<T, U> and then writing there Conteiner<N, M> .
I needed to create classes (Conteiner and his descendants) storing lists of classes inherited from A. It is necessary because each heir stores certain data, and containers are needed for their entry and withdrawal.
This code is necessary in order to quickly convert the data.

Andrey NOP 24.9k four 25 57 · Answer 1 · 2017-09-07T08:27:35

You can do by doing so:

 public class Conteiner<T, U> where T : B<U> where U : A { T[] list; public T this[int index] { get { return list[index]; } set { list[index] = value; } } public void Set<K,N,M>(Conteiner<T, U> conteiner) where K : Conteiner<N, M> where N : B<M> where M : A { list[0] = conteiner[0]; } }

Reduction of generic types <T>

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