Is it a better design to inherit from an abstract class or from an interface if the child classes ha-CodePudding

I have two classes B and C which share a common property a of type D.

class B
{
  public D a {get;set;}
  public E b {get;set;}
}

class C
{
  public D a {get;set;}
  public F c {get;set;}
}

I could make a

abstract class A 
{
  public D a {get;set;}
}

from which B and C inherits.

class B:A
{
  public E b {get;set;}
}

class C:A
{
  public F c {get;set;}
}

I also know that I will have a service with a method GetValue which returns an object of type A.

interface Service
{
  A GetValue();
}

The class A could also be an interface but then the property a had to be implemented double by B and C. The question is should I use interface or abstract for implementig A? To inherit from abstract class just for the reason that two classes have a common property seems to be not a good practice, but I am not sure.

CodePudding user response：

You can reflect both the common property a and method GetValue() in an abstract class. Keep in mind that in C your function signature cannot return abstract type. I also don't see how an interface could do anything for you in your example, as it would simply be empty.

CodePudding user response：

If you're using C# > 8.0 then you can create an interface with a default method implementation. This way you don't have to have an abstract class but at the same time you don't need to re-implement the shared method.