What are the characteristics of override in C#?

In C#, “override” is a modifier for a method that indicates that the derived class is rewriting (or overriding) a method with the same name in the base class. “Override” has the following characteristics:

1. The method must have the same name, parameter list, and return type as the virtual or abstract method in the base class.
2. The “override” keyword can only be used in derived classes and not in base classes or non-derived classes.
3. The overridden method must be declared as a virtual method (using the keyword virtual) or an abstract method (using the keyword abstract) in the base class.
4. The “override” keyword can be used to override virtual properties (using the “virtual” keyword) or abstract properties (using the “abstract” keyword) in a base class.
5. The overridden method can call the implementation in the base class using the base keyword.
6. The keyword “override” can be used to rewrite the ToString() and Equals() methods in the base class in order to customize the string representation and comparison logic of a custom class.
7. The overwritten method can have increased access modifiers, but cannot change the return type.
8. Overriding methods can throw exceptions, but they cannot throw more exceptions than the base class method.
9. The “override” keyword can be used with the “sealed” keyword to indicate that further derived classes are prohibited from overriding that method.

These characteristics make the “override” keyword an important mechanism for achieving polymorphism in C#, allowing derived classes to replace methods in the base class with their own implementation, providing more flexible and specific behavior.