Assigning child object to the base is possible, But if do the same with the collection it is not possible

Question

Assigning child object to the base is possible.

base1 b1 = new child1();

But if we do the same with the collection it is not possible, Why?

List<base1> libase = new List<child1>();

Any reference having this explanation is very helpful, please share

        public class base1
        {

        }
        public class child1 : base1
        {

        }
        static void Main(string[] args)
        {
            base1 b1 = new child1();
            List<base1> libase = new List<child1>();
            Console.Read();   
        }

@JornVernee Thanks, was not able to find out anything related to this — Amit Bisht, May 25 '17 at 11:05
@dahui The question is also tagged with Java, besides the explanation is pretty much the same. — Jorn Vernee, May 25 '17 at 11:05

score 1 · Accepted Answer · answered May 25 '17 at 11:06

In c# you can do such trick:

List<base1> libase = new List<base1>(new List<child1>());

Also, you can use Interface IEnumerable:

IEnumerable<base1> libase = new List<child1>();

Because it's declared as:

  public interface IEnumerable<out T> : IEnumerable
  {
    IEnumerator<T> GetEnumerator();
  }

out T it the most important.

When List is just:

public class List<T>
{}

About your question read more here Covariance and Contravariance in Generics

Assigning child object to the base is possible, But if do the same with the collection it is not possible

1 Answers1