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Understanding the Difference Between Abstract Classes and Interfaces in C#

Abstract classes and interfaces are key components in C# programming that facilitate code reusability and abstraction. The primary difference between the two lies in their design and usage.

Abstract Classes

An abstract class is a class that cannot be instantiated on its own and is often used as a blueprint for other classes. It may contain abstract methods which must be implemented by any class that inherits from it. Abstract classes can also contain concrete methods, fields, and properties.

Interfaces

Interfaces, on the other hand, are similar to abstract classes in that they define a contract for implementing classes. However, interfaces cannot have any implementation details; they only contain method signatures, properties, events, and indexers that must be implemented by classes that inherit from them.

Example Usage in a .NET Project

In a .NET project, you might choose to use an abstract class when you want to provide a common implementation for a set of related classes. For instance, if you have a hierarchy of animals with shared behaviors (e.g., eat, sleep, move), you can create an abstract class Animal with abstract methods for these behaviors that each specific animal class must implement.

Conversely, interfaces are ideal when you want to define a contract that multiple unrelated classes can implement. For example, if you have different types of vehicles such as car, bike, and airplane, each implementing a specific interface IVehicle with methods like Start() and Stop(), you can ensure consistency in their functionality without relying on inheritance.

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