C# Notes (General + .NET Context)

1. C# Language Basics

• Type-Safe, Object-Oriented Language
  • Developed by Microsoft as part of the .NET platform.
  • Strongly typed (variables must match their declared type).
  • Supports OOP pillars: Encapsulation, Inheritance, Polymorphism, Abstraction.
• Common Data Types
  • Value types: int, double, bool, char, struct
  • Reference types: string, class, object, array, interface
  • Nullable types: int?, bool? (helpful when working with databases).
• Operators
  • Arithmetic (+, , , /, %), Logical (&&, ||, !), Comparison (==, !=, <, >).
• Control Flow
  • if/else, switch, for, foreach, while, do while, break, continue.

2. Object-Oriented Programming in C#

• Classes & Objects

  • Defined with class.

  • Example:

    public class Product {
        public int Id { get; set; }
        public string Name { get; set; }
    }
    
    

• Constructors

  • Special methods that initialize objects.
  • Can be overloaded.

• Properties

  • Encapsulation of fields using { get; set; }.
  • Auto-properties simplify syntax.

• Methods

  • Functions inside classes. Support parameters, return types, and overloading.

• Inheritance

  • One class derives from another using :.

  • Example:

    public class Animal { public void Eat() {} }
    public class Dog : Animal { public void Bark() {} }
    
    

• Polymorphism

  • Virtual/override methods.
  • Interfaces allow multiple behaviors across unrelated classes.

3. Advanced Features

• Generics

  • Allow type safety without specifying concrete types.
  • Example: List<T>, Dictionary<TKey, TValue>.

• Interfaces

  • Define a contract without implementation.

  • Example:

    public interface IRepository<T> {
        void Add(T entity);
        T GetById(int id);
    }
    
    

• Abstract Classes

  • Cannot be instantiated; provide partial implementation.