Derive Abstact Property

Question

I have a base class that has an abstract property:

public class BottomClass {
  public abstract string Name {get;set;}
}

I now have a class that derives from that:

public class MiddleClass:BottomClass {
  public override string Name {get;set;}
}

what I now want is that the "MiddleClass" itself defines that property as abstract so that a class deriving from that will be forced to implement the property. The following code is not working that way:

public class MiddleClass:BottomClass {
  public abstract override string Name {get;set;} // Not possible that way
}

public class TopClass:MiddleClass {
  public override string Name {get;set;} ="tothetop";
}

Is there a way to achieve what I want?

You dont want to do things like `TopClass : BottomClass` right? — michasaucer, Feb 12 '19 at 10:27
Both `BottomClass` and `MiddleClass` classes must be declared `abstract` (since they declare `abstract` properies) — Dmitry Bychenko, Feb 12 '19 at 10:27
And then https://stackoverflow.com/questions/13518381/overriding-abstract-methods-in-an-inherited-abstract-class for what to do after marking the middle class abstract. — Rawling, Feb 12 '19 at 10:28
What's the point of `MiddleClass` "re-declaring" that the property is abstract? - just don't implement it at all. — Damien_The_Unbeliever, Feb 12 '19 at 10:29
Abstract methods can only be added to Abstract classes in C#. You cant add abstract methods in a non-abstract class in C#. — S2S2, Feb 12 '19 at 10:29

score 2 · Accepted Answer · answered Feb 12 '19 at 10:51

If you define a property as abstract, you have to implement it in some non abstract class. So the only possible way to have the property in both classes is

public abstract class BottomClass
{
    public abstract string NameB { get; set; }
}

public abstract class MiddleClass : BottomClass
{
    public abstract string NameM { get; set; } 
}

public class TopClass : MiddleClass {
    public override string NameB { get; set; }
    public override string NameM { get; set; }
}

As far as I can understand, your intention is to have 'Name' property in MiddleClass.

Or don't implement it, as Damien commented above.

score 1 · Answer 2 · answered Feb 12 '19 at 11:33

Throw exceptions if you have some reason not to make the class abstract.

public class MiddleClass:BottomClass
{
    public override string Name
    {
        get => throw new NotImplementedException();
        set => throw new NotImplementedException();
    }
}

Derive Abstact Property

2 Answers2