When to Use Abstract Class and Interface

In this article we are going to discuss when to use Abstract and Interface in C#. There are many blogs, articles are available on the internet regarding it but in this particular article I will try to explain to you with as much as simple.

Choosing between an interface and an abstract class in C# depends on the specific needs and design considerations of your application. Here are some guidelines to help you decide when to use each:

When to Use an Interface

1. Multiple Inheritance: Use an interface when you need to support multiple inheritance. A class can implement multiple interfaces but can inherit from only one base class.

2. Behavior Contracts: Use interfaces to define a contract for behaviors without enforcing any common implementation. Interfaces specify what a class must do, not how it should do it.

3. Loose Coupling: Interfaces help to achieve loose coupling between classes. You can change the implementation of an interface without affecting the code that depends on it.

4. Plugin and Extensibility Patterns: Interfaces are ideal for defining plugins or extensions where the implementing classes can vary widely.

5. Pure Abstraction: When you need pure abstraction with no default implementation, use interfaces.

When to Use an Abstract Class

1. Shared Code: Use an abstract class when you want to provide some common functionality that can be shared among all derived classes. Abstract classes can contain both abstract methods (which must be implemented by derived classes) and concrete methods (which provide default behavior).

2. Base Class for Hierarchy: If you are creating a base class for a closely related set of objects and expect to provide common code and state, use an abstract class.

3. Versioning and Evolution: Abstract classes are easier to evolve over time. If you add a new method to an abstract class, you can provide a default implementation, which won't break existing derived classes.

4. Access Modifiers: Abstract classes can have access modifiers for members, allowing you to control the visibility of methods and properties. Interfaces cannot have access modifiers for their members (all interface members are public by default).