What is difference between abstract class and interface and when should we use interface and abstract class?

Although you can generate derivatives from this, you cannot create an object of the abstract class.

Either abstract or non-abstract methods can be found in an abstract class. There is no implementation for abstract members in the abstract class; nevertheless, a derived class must supply one.

Both abstract and non-abstract members can be found in an abstract class. The members of an interface, however, must all override the members of its derived class because all interface elements are implicitly abstract in nature.

Similar to defining an interface, declaring an abstract class includes all of its abstract members. Specifically, we can say that an interface is a class that has all abstract members.

Classes can only descend from one base class, therefore if you wish to use abstract classes to give a bunch of classes polymorphism, they must all all descend from that base class.

Members that have already been put into practise may also be offered by abstract classes. With an abstract class, you can guarantee some degree of equivalent functionality, but not with an interface.

Here are some suggestions to help you choose between using an abstract class or an interface to offer polymorphism for your components.

1) Make an abstract class if you plan to produce several iterations of your component. Versioning your components is made simple and straightforward using abstract classes. All inheriting classes are automatically updated with the change when the base class is modified. Conversely, once they have been created, interfaces cannot be altered. If an interface needs to be updated, a brand-new interface must be made.

2. Use an interface if the functionality you are developing will be helpful across a variety of unrelated items. While interfaces are best suited for giving common functionality to unconnected classes, abstract classes should be utilized primarily for things that are tightly related.

3. Use interfaces for creating brief, compact pieces of functionality. Use an abstract class when constructing huge functional units.

4. Use an abstract class if you want to give all component implementations common, implemented functionality. In contrast to interfaces, which include no implementation for any members, abstract classes allow you to partially implement your class.