Classes

.NET Interfaces

Defining Interfaces

.NET interfaces define contracts with default implementations.

Understanding Interfaces in .NET

Interfaces in .NET are used to define a contract that classes or structs can implement. These contracts ensure that certain methods, properties, events, or indexers are available in implementing types. Interfaces can include default implementations, which allows them to provide a base behavior that can be overridden by implementing classes.

Defining an Interface

To define an interface in .NET, use the interface keyword followed by the interface name. Interface names typically begin with the letter 'I'. Here's a simple example:

Implementing an Interface

When a class implements an interface, it must provide concrete implementations for all the interface's members. Below is an example of a class implementing the IShape interface:

Default Implementations in Interfaces

Starting with C# 8.0, interfaces can have default implementations for its members. This allows developers to add new methods to interfaces without breaking existing implementations. Here's how you can provide a default implementation:

Using Interfaces in Applications

Interfaces are particularly useful in applications for achieving loose coupling and enhancing testability. By programming to an interface, you can easily swap out implementations without changing the code that uses the interface. Here’s an example of using the IShape interface:

Benefits of Using Interfaces

Using interfaces provides several benefits:

Abstraction: Interfaces allow you to define methods without implementing them, which provides a clear separation of what a class can do and how it does it.
Multiple Inheritance: A class can implement multiple interfaces, allowing for a form of multiple inheritance.
Decoupling: Interfaces help to decouple code and reduce dependencies, making it easier to maintain and test.

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