CODEWITHSUNDEEP
c#interface
user9623401
user9623401

Reputation:

explicit implementation doesn't work in my case

I don't quite understand how explicit implementation works, so I made a mockup

public class ShoppingCart : IEnumerable<Product>
{
   public IEnumerator<Product> GetEnumerator()
   {
      return Products.GetEnumerator(); 
   }
   IEnumerator IEnumerable.GetEnumerator() //why 'public' is not needed?
   {
      return GetEnumerator(); // why there is not any error here?
   }
}

Below is my mockup:

class MockUp: Ilayer1
  {
    public string testMethod()
    {
      return "Layer1";
    }

    string Ilayer2.testMethod()  // error, not all code path return a value
    {
      testMethod();
    }
  }

  interface Ilayer1 : Ilayer2
  {
    string testMethod();
  }

  interface Ilayer2
  {
    string testMethod();
  }

but I have a compilation error, but why there is no error for ShoppingCart?

And how can I make my MockUp class work?

Upvotes: 0

Views: 57

Answers (1)

Dmitrii Bychenko
Dmitrii Bychenko

Reputation: 186668

Let me answer the questions one after one:

why 'public' is not needed?

Since if we put public we'll have an ambiguity: 

public IEnumerator<Product> GetEnumerator() {...}

public IEnumerator IEnumerable.GetEnumerator() {...}

And in case of ShoppingCart.GetEnumerator(); which method will be executed? That's why explicit interface implementation is effectively private

// public
public IEnumerator<Product> GetEnumerator() {...}

// private
IEnumerator IEnumerable.GetEnumerator() {...}

So far so good in case of ShoppingCart.GetEnumerator(); we call the only public method (with no ambiguity). In case of (ShoppingCart as IEnumerable).GetEnumerator(); we call an interface implementation whatever it is (again we have only one method which fits).

I have a compilation error, but why there is no error for ShoppingCart?

string Ilayer2.testMethod()  // error, not all code path return a value
{
  testMethod();
}

The method should return string, but it doesn't do it. Add return:

string Ilayer2.testMethod()  // error, not all code path return a value
{
   return testMethod();
}

Or even

string Ilayer2.testMethod() => testMethod();

Upvotes: 0

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