C# Interface and base classes

Question

I have a C# interface, and a concrete class that implements that interface. I now want to create another class that implements that interface. Simple enough.

However, most methods will be exactly the same in the classes, and only a couple of methods will actually change.

I don't want to duplicate all of the logic in my 2nd class that is contained in my first.

How do I create the 2nd class, and use the logic in my first class except for the extra stuff?

My interface is called IEventRepository, and my 1st class is called BaseEvents. I now want to create a new class called FooBarEvents.

My class definition for FooBarEvents is:

public class FooBarEvents : BaseEvents, IEventRepository

My intention was to then use the return base.Method() in each method that duplicates the code.

I'm assuming this isn't correct?

Answer 1

The following code shows how to provide a common implementation of some interface methods with an abstract base class, and provide custom implementations for others.

public interface IEventRepository
{
  void Method1();
  void Method2();
}

public abstract class BaseEvents : IEventRepository
{
  public void Method1() 
  {
    Console.WriteLine("This is shared functionality");
  }

  public abstract void Method2();
}

public class Implementation1 : BaseEvents
{
  override public void Method2()
  {
    Console.WriteLine("Impl1.Method2");
  }
}

public class Implementation2 : BaseEvents
{
  override public void Method2()
  {
    Console.WriteLine("Impl2.Method2");
  }
}

public class Program
{
  static void Main(string[] args)
  {
    var implementations = new List<IEventRepository> { new Implementation1(), new Implementation2() };

    foreach (var i in implementations) 
    {
       Console.WriteLine(i.GetType().Name);
       Console.Write("\t");
       i.Method1();  // writes 'This is shared functionality'

       Console.Write("\t");
       i.Method2(); // writes type specific message
    }
  }

}