.NET Framework and C# Basics

1. History and Overview of .NET Framework

Developed by Microsoft (2002) to provide a consistent programming model for Windows apps.
Supports multiple languages (C#, VB.NET, F#).
Runs on Common Language Runtime (CLR), ensuring language interoperability.
Provides a Base Class Library (BCL) for I/O, collections, networking, etc.

Key Features:

Cross-language interoperability (all .NET languages compile to IL).
Automatic memory management (Garbage Collection).
Security (Code Access Security, role-based security).
Versioning and deployment support.
Supports desktop, web, mobile, and cloud apps.

Diagram (link): .NET Architecture

2. Components and Versions

Main Components:

CLR (Common Language Runtime)
- Executes code, manages memory, type safety, exception handling, security.
BCL (Base Class Library)
- Pre-built classes for collections, file handling, XML, threading, etc.
CLS (Common Language Specification)
- Defines a set of rules all .NET languages must follow.
CTS (Common Type System)
- Ensures type compatibility across languages.
ASP.NET → Web development
ADO.NET / Entity Framework → Database access
WPF / WinForms → Desktop UI

Versions Timeline (major):

.NET Framework 1.0 → 2002
.NET Framework 2.0 → 2005
.NET Framework 3.5 → 2007 (LINQ, WCF, WPF)
.NET Framework 4.0/4.5 → 2010/2012
.NET Core (2016) → cross-platform
.NET 5 (2020) → unified platform
Latest → .NET 8 (2023)

Diagram (link): CLR & Components

3. Introduction to C#

3.1 C# Language

Object-oriented, type-safe, modern programming language by Microsoft.
Runs on CLR, ensuring safety and portability.
Syntax similar to C++ and Java.

Example:

using System;
 
class HelloWorld
{
    static void Main()
    {
        Console.WriteLine("Hello, C#!");
    }
}

3.2 C# Language Elements

Namespace: Container for classes.
Class: Blueprint of objects.
Method: Function inside class.
Variable: Stores data.
Access Modifiers: public, private, protected, internal.

3.3 Data Types

Value Types

Store actual value.
Examples: int, char, bool, float, struct.
Stored in stack.

int x = 10;
char c = 'A';

Reference Types

Store reference (address) to data.
Examples: string, object, arrays, class, interface.
Stored in heap.

string name = "Shivam";
object obj = name;

3.4 Boxing and Unboxing

Boxing → Converting value type → reference type.
Unboxing → Converting reference type → value type.

Example:

int val = 100;          // value type
object obj = val;       // boxing
int num = (int)obj;     // unboxing

3.5 Enum and Constant

Enum → Collection of named constants.

enum Days { Sun, Mon, Tue, Wed, Thu, Fri, Sat }
Days today = Days.Mon;

Constant → Fixed value, cannot be changed.

const double PI = 3.14159;

3.6 Operators & Control Statements

Operators:

Arithmetic: + - * / %
Relational: == != > < >= <=
Logical: && || !
Assignment: = += -=

Control Statements:

if (x > 10)
    Console.WriteLine("Large");
else
    Console.WriteLine("Small");
 
for (int i = 0; i < 5; i++)
    Console.WriteLine(i);
 
switch (day)
{
    case 1: Console.WriteLine("Mon"); break;
    default: Console.WriteLine("Other day"); break;
}

3.7 Working with Arrays and Strings

Array Example:

int[] arr = { 1, 2, 3, 4 };
foreach (int i in arr)
    Console.WriteLine(i);

String Example:

string s1 = "Hello";
string s2 = "World";
string result = s1 + " " + s2;  // concatenation

3.8 Pass by Value and Pass by Reference

Pass by Value (default) → Copy of variable passed.

void Square(int n) { n = n * n; }

Pass by Reference (using ref) → Actual variable passed.

void Square(ref int n) { n = n * n; }

3.9 Parameters, Variable Length Parameter

Normal Parameter:

void Add(int a, int b) { Console.WriteLine(a + b); }

Optional Parameter:

void Print(string name = "Guest") { Console.WriteLine("Hello " + name); }

Variable Length Parameter (params):

void Sum(params int[] nums)
{
    int total = 0;
    foreach (int n in nums) total += n;
    Console.WriteLine("Sum: " + total);
}
 
Sum(1, 2, 3, 4);  // Output: Sum: 10

notes-shivam

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1. Dot NET Framework and C-sharp Basics