C＃与接口的多重继承

Question

public interface IA
{
  void DoSomething();
  void Calculate();

}

public interface IB
{
  void DoSomethingElse();
  void Calculate();
}

public class A : IA
{
  void DoSomething() { }
  void Calculate() {}
}

public class B : IB
{
  void DoSomethingElse() { }
  void Calculate() {}
}

public class C : IA, IB
{

    //How can I implement Calculate() in class B and DoSomething() in class A?
}

How can I avoid duplicate code in class C. Reference: How to simulate multiple inheritance in C# . I don't want to write the full methods again in class C. Thanks for any help.

Answer 1

Note that you are not achieving multiple inheritance at all. C# has singular inheritance. You are implementing multiple interfaces.

There is absolutely no reason why you cannot implement the interfaces in classes A and B , and then have B derive from A and C derive from B. The method implementations from the interfaces can even be abstract, which forces the child class to do the implementation. If you follow this approach then you can still pass C around as IA or IB simply by casting or using the as keyword.

You can also have interface IB "inherit" ¹ (implement) IA , which means anything that implements IB must also implement IA .

¹ When IB derives from IA it isn't inheritance like it is at the class level, it is actually still implementation. So IB implements IA , it doesn't inherit it.

Answer 2

Assuming that IA.Calculate() is not the same as IB.Calculate() and you therefore can't just make IB inherit from IA , you can implement both interfaces in C by delegating execution on private instances of A and B :

public class C : IA, IB
{
    private A _a;
    private B _b;

    public C()
    {
        this._a = new A();
        this._b = new B();
    }

    public void DoSomething()
    {
        this._a.DoSomething();
    }
    void IA.Calculate()
    {
        this._a.Calculate();
    }
    public void DoSomethingElse()
    {
        this._b.DoSomethingElse();
    }
    void IB.Calculate()
    {
        this._b.Calculate();
    }
}