C# casting child class to parent interface with type parameters fails

Asked Aug 31 '18 at 10:35

Active Aug 31 '18 at 10:35

Viewed 28 times

Having defined the following:

public interface IFoo { }
public interface IBar<IFoo> { }

public class Foo : IFoo { }
public class Bar : IBar<Foo> { }

This line throws error:

IBar<IFoo> test = (IBar<IFoo>) new Bar();

"Unable to cast object of type 'Bar' to type 'IBar'1[IFoo]'

Why is that? How can I resolve this issue?

asked Aug 31 '18 at 10:35

If you define the second interface as `public interface IBar` you can cast it. Google 'covariance'. – Hans Kilian Aug 31 '18 at 10:49
Also, the question set up as the answer is a different case. That one doesn't have interfaces like this one does. – Hans Kilian Aug 31 '18 at 10:51

0 Answers0