Abstract Class vs Interface in .Net

In .Net, an abstract class is a class that cannot be instantiated on its own and is intended to be extended by other classes. It can contain both abstract (unimplemented) and concrete (implemented) members. On the other hand, an interface is a contract that defines a set of members that a class must implement. Classes can implement multiple interfaces but can only inherit from a single abstract class.

The main difference between an abstract class and an interface in .Net is that an abstract class can have implemented methods, fields, and constructors, while an interface can only have method signatures. Additionally, an abstract class can provide default behavior for some methods that derived classes can override, whereas an interface cannot contain any implementation.

When choosing between an abstract class and an interface, consider whether you need to define a common base implementation or if you need to define a contract for multiple classes to implement. Abstract classes are useful when you want to provide a common implementation for related classes, while interfaces are beneficial for defining a contract that multiple unrelated classes can fulfill.