C# How to use interfaces

Question

This is a relatively straight forward question. But I was wondering what the correct usage is for accessing a method inside a separate project through the use of an interface.

Answer 1

• You never instantiate ITest test, you only declare it.
• Your Test class doesn't inherit from the interface.

You need to update your class declaration

public class Test : ITest // interface inheritance 
{

And in your controller, instantiate test.

ITest test = new Test();

As you get further along, you'll want to explore techniques for injecting the Test instance into the controller so that you do not have a hard dependency upon it, but just on the interface ITest. A comment mentions IoC, or Inversion of Control, but you should look into various Dependency Inversion techniques techniques (IoC is one of them, dependency injection, etc).