Inheritance and Polymorphism in OOP

Object-Oriented Programming Concepts

• A method in a derived class that has the same signature as a base class method hides the base method.
• A method intended to be overridden is referred to as a virtual method.
• Overriding is the mechanism that allows derived classes to provide different implementations of the same method.
• A virtual method cannot be private; it must be accessible to allow overriding.
• The signature of virtual and override methods must match exactly in both name and parameters.

Access Modifiers

• The protected access modifier allows access to class members from the class itself and derived classes.
• To extend a type quickly without impacting existing code, utilize extension methods.
• Extension methods are defined in a static class and allow adding static methods to existing types.
• The first parameter of an extension method must specify the type to which the method applies.

Interfaces and Abstract Classes

• An interface does not contain any implementation; it specifies the methods and properties that implementing classes must fulfill.
• Interfaces provide a way to separate method signatures from their implementations.
• Both interfaces and abstract classes share similarities in defining methods that must be implemented.

Inheritance

• Inheritance helps avoid code repetition by allowing classes with common features to relate through a parent-child relationship.
• In C#, inheritance is a relationship between classes and can only apply to classes, not structures.
• Use the class DerivedClass : BaseClass {...} syntax for defining derived classes in C#.
• C# inheritance is always implicitly public, meaning it allows access unless specified otherwise.

Constructors and Base Class Calls

• Initialization of fields within a class is performed in a constructor.
• The base keyword is used to call a base class constructor in derived classes.
• If a derived class does not explicitly call a base class constructor, the compiler automatically calls the base class’s default constructor.

Method Overloading and Variadic Methods

• Overloading occurs when multiple methods share the same name but differ in parameters.
• A variadic method accepts a variable number of arguments, allowing for flexible method calls.
• The ArgumentException class is used to handle illegal arguments supplied to methods.
• The params keyword cannot be used with multidimensional arrays, and overloads cannot solely rely on the params keyword.

Method Calls and Validations

• Specifying the ref or out modifier with params arrays is not allowed.
• Methods cannot share the same name and differ only by using the params keyword in different contexts if combined with ref or out.
• Valid calls to a method with params include multiple argument entries, but using unsupported types or formats may lead to compilation errors.