Derived type of generics C#

Question

I have the following code

interface IEncryption{}
class EncryptionA : IEncryption {}
class EncryptionHandler<T> where T: IEncryption{}
class EncryptionMenu
{
    public EncryptionMenu(EncryptionHandler<IEncryption> encryption){}
}

void main()
{
   EncryptionMenu encryptionMenu = new EncryptionMenu(new EncryptionHandler<EncryptionA>()); // Error
}

I get

"Argument type 'EncryptionHandler< EncryptionA>' is not assignable to parameter type 'EncryptionHandler< IEncryption>'"

and I cant understand why it cant convert it even though EncryptionA implements IEncryption and is supposed to cast it. I tried to make the EncryptionMenu generic too but it makes the same error bubble upwards and complicates the code.

Answer 1

You have to mark T as out: class EncryptionHandler where T: IEncryption{}

its about c# co/contravariance