How to remove in a child class a method inherited from a parent class?

Question

I have ChildClassA, ChildClassB and ChildClassC.

They all inherit from ParentClass.

How can I declare an already implemented method for A and B, but which is not needed in C?

1. Implementation in ParentClass doesnt make sense, since I only need it in A and B.

2. C# does not support multiple inheritance (if this would even be my best option).

3. An interface is not helping me because I cannot implement a method there.

Answer 1

What you are looking for is a form of Composition:

using System;
                    
public class Program
{
    public static void Main()
    {
        var a = new ChildA();
        a.SomeMethod();
        
        var b = new ChildB();
        b.SomeMethod();
        
        var c = new ChildC();
        // c.SomeMethod(); Doesn't have SomeMethod
    }
}

public class ParentClass
{
}

public class ChildA : ParentClass, IHavingSomeMethod
{
   private readonly IHavingSomeMethod _sms;
   
   public ChildA()
   {
       _sms = new HavingSomeMethodService(); // Have it injected instead!
   }
   
   public void SomeMethod() => _sms.SomeMethod();
}

public class ChildB : ParentClass, IHavingSomeMethod
{
   private readonly IHavingSomeMethod _sms;
   
   public ChildB()
   {
       _sms = new HavingSomeMethodService(); // Have it injected instead!
   }
   
   public void SomeMethod() => _sms.SomeMethod();
}

public class ChildC : ParentClass
{
}

public interface IHavingSomeMethod
{
    void SomeMethod();
}

public class HavingSomeMethodService: IHavingSomeMethod
{
   public void SomeMethod()
   {
      Console.WriteLine("SomeMethod");
   }
}

Try it out

Answer 2

ParentClass inherits to

• CommonClass

• and ChildClassC

CommonClass inherits to

• ChildClassA
• and ChildClassB

CommonClass defines the method