Interfaces

Introduction to Interfaces

An interface in .NET defines a contract that classes can implement. It specifies a set of methods, properties, events, or indexers that implementing classes must provide. Interfaces enable polymorphism and decouple the implementation from the interface definition.

Defining an Interface

In .NET, interfaces are declared using the interface keyword. They contain method and property signatures but no implementation.

public interface IShape {
    void Draw();
    double Area { get; }
}
    

Implementing Interfaces

Classes that implement an interface must provide implementations for all members defined in the interface.

public class Circle : IShape {
    public void Draw() {
        // Implement Draw method
    }

    public double Area {
        get {
            // Calculate area of circle
            return Math.PI * Radius * Radius;
        }
    }

    public double Radius { get; set; }
}
    

Using Interfaces for Polymorphism

Interfaces support polymorphism, allowing objects of different classes to be treated as instances of the same interface.

IShape shape = new Circle();
shape.Draw();
double area = shape.Area;
    

Interface Inheritance

Interfaces can inherit from other interfaces, enabling the creation of hierarchies of interfaces.

public interface IMovable {
    void Move();
}

public interface IResizable : IMovable {
    void Resize();
}
    

Conclusion

Interfaces in .NET provide a powerful mechanism for defining contracts that classes must adhere to. They facilitate code reusability, polymorphism, and separation of concerns, making applications more flexible and maintainable.