How many types of classes in .Net?

The class is one of the two basic encapsulation constructs in C# (the other being the struct). Every executable statement must be placed inside a class or struct. Classes define reference types that are the basic building blocks of C# programs, and they are the architectural blueprint for the “objects” in OOP.
Types of classes :-

1. Abstract: An instance of the class cannot be created. Usually this means the class is intended to serve as a base class. Abstract methods must be overridden in a derived class. If any method of a class is abstract, the entire class must be declared as abstract.
2. Sealed: The class cannot serve as a base class for another class (it can’t be derived from). A class cannot be both abstract and sealed. Sealed methods are methods that override an inherited virtual method having the same signature. When a method is sealed, it cannot be overridden in a derived class. Sealed classes are used to restrict the inheritance feature of object oriented programming. Once a class is defined as sealed class, this class cannot be inherited.
3. New: Used only with nested classes. “New” indicates that the class hides an inherited member of the same name.

assembly:-

• Constructor Modifiers: A class defines data members, methods and nested types. A constructor is a special method that is normally used to initialize the data members of a class, and its name is always the same as the name of the class. Constructors have no return value, and any number of constructors can be defined within a class. If no constructor is defined, the C# compiler provides a default constructor having no parameters.

• Methods: Methods are always defined within the bounds of a class or struct. Methods can be instance (called as an instance of the type within which the method is defined) or static, where the method is associated with the type itself. Methods can be declared as virtual, abstract, or sealed. Methods can be overloaded, overridden and hidden.

Virtual methods can be overridden by a derived class using the override keyword.