C#接口和类继承

Question

I have a problem with using interface methods in my object. I'l giva a quick example without all the inplementations.

public class Item{}
public interface IFruit
{
      void MethodExample();
}

public class Apple : Item, IFruit
{
    public void IFruit.MethodExample(){}
}

// put this in a run method somewhere
var example_item = new Apple();

//Here comes the problem.
example_item.MethodExample();
// this will return an error saying that it cant find the method.

Anyway to do this? I know for a fact that it implements the i_fruit. And has the method. Yet i cant access it?

Answer 1

First of all, please read c# naming conventions. Secondly, you have implemented i_fruit interface explicitly, you should cast your example_item into i_fruit or more common way is to implement i_fruit interface implicitly. Please read: https://blogs.msdn.microsoft.com/mhop/2006/12/13/implicit-and-explicit-interface-implementations/

Implicit implementation example:

public class Apple : Item, IFruit
{
   public MethodExample(){}
}

On the other hand if you want to stick to explicit implementation, then you should change your code into this:

IFruit example_item;
example_item = new Apple();

Answer 2

the syntax in your provided example does not exactly look like C#, but here is a simple example, that looks similar to yours. The class Item does not have an ExampleMethod, but Apple does, because it implements the interface IFruit. You can, however, use the as keyword to cast the object into something else temporarily, and thereby get access to the ExampleMethod. A common way to deal with this type of situation is seen in the example with exampleFruit . Hope this helps.

using System;

namespace StackOverflowInterfaces
{
    class Item { }
    interface IFruit
    {
        void ExampleMethod();
    }

    class Apple : Item, IFruit
    {
        public void ExampleMethod()
        {
            throw new NotImplementedException();
        }
    }

    class MainClass
    {
        public static void Main()
        {
            Item exampleItem = new Apple();
            // exampleItem.ExampleMethod(); -- DOES NOT WORK, because Item does not implement IFruit
            (exampleItem as IFruit).ExampleMethod();
            (exampleItem as Apple).ExampleMethod();

            IFruit exampleFruit = new Apple();
            exampleFruit.ExampleMethod();

            Apple exampleApple = new Apple();
            exampleApple.ExampleMethod();

        }
    }
}