There are some advanced concepts related to abstract classes in C# that we are going to learn :
Abstract classes can have constructors: Contrary to popular belief, abstract classes can have constructors. The constructor of an abstract class can be called from derived classes when they are instantiated. However, you cannot directly instantiate an abstract class.
Abstract classes can be used to define interfaces: Abstract classes can be used to define interfaces with default implementations of methods. In C#, interfaces cannot have implementations, but abstract classes can. By using an abstract class to define an interface, you can provide a default implementation for methods that are common to all implementing classes.
Abstract classes can implement interfaces: Abstract classes can implement interfaces just like any other class. When an abstract class implements an interface, it must implement all the methods defined in the interface, just like any other class.
Abstract classes can be used to enforce a contract: Abstract classes can be used to enforce a contract on derived classes. By defining an abstract class with certain methods and properties, you can ensure that any class that derives from it will have those methods and properties. This can be useful when you want to ensure that all derived classes implement certain functionality.
Abstract classes can be sealed: You can prevent derived classes from further inheriting an abstract class by marking it as sealed. This means that the abstract class cannot be further extended or overridden.
Abstract classes can have fields: Abstract classes can have fields just like any other class. However, the fields cannot be directly accessed by derived classes. If you want to expose a field to derived classes, you must define it as a protected field.