• Value Types
• Reference Types

Value Type →

• Struct
• Enum
• All Built-In data types are value data types expect (String - System.Object)
• Any value type allocated in Stack.
• int x; → allocation of 4 uninitialized bytes in stack.
• int = Int32
• Int32 → base class library (BCL) for int
• y = x; → copy the value of x and assign it to y
• ++x; → does not affect y after assignment

int x;
///allocation 4 uninitialized bytes in stack
///int : c# keyword

x = 5;

int32 y;
/// int64 bcl struct
///allocation 4 uninitialized bytes in stack

y = x;
++x;

console.writeline(x);
console.writeline(y);

Reference Type →

• Class - String - System.Object
• System.Object → all data types inherits from this class for 2 reasons:
  • generics was invented in 2005 so from 2002 to 2005 System.Object was used for every thing.
  • set of behaviors should be supported in all Data Types:
    • Public Virtual String ToString(); → return object state (values) in string form
    • Public Virtual int GetHashCode(); -> return object identity (unique identifier)
    • public virtual bool Equals (Object O2); -> to check equality
    • public type GetType(); -> return data type
• Object O1; → zero bytes have been allocated in Heap.
• O1 = new Object();
  • new (IL -> newOBJ) →
    • allocate required numbers of bytes in Heap (Object Size + CLR Overhead Variables)
    • initialize (cross out) allocated byte
    • call constructor if exits
    • assign reference to new allocated object
• Object O2 = new Object();
• O2 = O1; -> O1,O2 will share same object identity (O1 identity) and O2 will be unReachable Location (garbage) and will be deleted when garbage collector applied on Heap

Object O1;
///Zero Bytes have been Allocated in Heap
O1 = new object();
///new (IL newObj)
///1.Allocate Required # of Bytes in Heap
///(Object Size + CLR Overhead Variables)
///2.Initialize(cross out ) allocted Bytes
///3.Call userdefined Ctor if exists
///4.Assign Refrence to newely allocated Object

//object O2 = new object();
object O2 = new(); ///C# 9.0 Syntax Sugar 

Console.WriteLine(O1.GetHashCode());
Console.WriteLine(O2.GetHashCode());

O2 = O1;
Console.WriteLine("After =");
Console.WriteLine(O1.GetHashCode());
Console.WriteLine(O2.GetHashCode());

///O2 , O1 Same Object , same identity  

• int x; → allocation of 4 uninitialized bytes in stack.
• string str; → it does not know how many bytes to allocate

String Formatting →

int X = 17;

float MyVar = 15.3f;
double MyVar02 = 1456.321;
decimal MyV = 15.3M;

int X = 1_000_000; //_ : Discards
X = 0x_00_00_FA_12; //Hex
byte y = 0b_0101_1100; //Binary

int X, Y;

X = int.Parse(Console.ReadLine());
Y = Convert.ToInt32(Console.ReadLine());

///C 
///printf ("%i + %i = %i" , X , Y , X+Y);

//String Msg = string.Format("Equation : {0} + {1} = {2}", X, Y, X + Y);
//Console.WriteLine(Msg);

//Console.WriteLine("Equation : {0} + {1} = {2}", X, Y, X + Y);

//string Msg = string.Format($"Equation : {X} + {Y} = {X + Y}");
/////$ : String Manipulation Operator
//Console.WriteLine(Msg);

Console.WriteLine($"Equation : {X,5}+{Y,-5}={X + Y:X}");

If & Switch Ex01 →

int X = 5;

/ Not Valid C# Code
if (X) ;
if (1) ;
if (X = 3) ;

if (X == 3)
    Console.WriteLine("Three"); ; ///Valid

X = int.Parse(Console.ReadLine());
if (X == 1)
    Console.WriteLine("Jan");
else if (X == 2)
    Console.WriteLine("Feb");
else if (X == 3)
    Console.WriteLine("Mar");
else
    Console.WriteLine("Not in Q01");

switch (X) // jump table becuz its num cases
{
    case 1:
        Console.WriteLine("Jan");
        break;
    case 2:
        Console.WriteLine("Feb");
        break;
    case 3:
        Console.WriteLine("Mar");
        break;
    default:
        Console.WriteLine("Not in Q03");
        break;
}

String str = Console.ReadLine();

switch (str)
{
    case "a":
    case "A":
        Console.WriteLine("Option 01");
        break;

    case "B":
    case "b":
        Console.WriteLine("Option 02");
        break;

    case "c":
    case "C":
        Console.WriteLine("Option 03");
        break;
}

switch (str)
{
    case "1":
        Console.WriteLine("Jan");
        break;

    case "2":
        Console.WriteLine("Feb");
        break;
    case "3":
        Console.WriteLine("Mar");
        break;
    case "4":
        Console.WriteLine("Apr");
        break;
    case "5":
        Console.WriteLine("May");
        break;
    case "6":
        Console.WriteLine("Jun");
        break;
    case "7":
        Console.WriteLine("Jul");
        break;

    default:
        Console.WriteLine("NA");
        break;
}

Switch Ex02 →

int Value = 3000;

switch (Value)
{
    case 3000:
        Console.WriteLine("Option 03");
        Console.WriteLine("Option 02");
        Console.WriteLine("Option 01");
        break;
    case 2000:
        Console.WriteLine("Option 02");
        Console.WriteLine("Option 01");
        break;

    case 1000:
        Console.WriteLine("Option 01");
        break;
    default:
        Console.WriteLine("NA");
        break;
}

switch (Value)
{
    case 3000:
        Console.WriteLine("Option 03");
        //Console.WriteLine("Option 02");
        //Console.WriteLine("Option 01");
        goto case 2000;
    //break;
    case 2000:
        Console.WriteLine("Option 02");
        //Console.WriteLine("Option 01");
        goto case 1000;
    //break;
    case 1000:
        Console.WriteLine("Option 01");
        break;
    default:
        Console.WriteLine("NA");
        break;
}

Block Statement →

//object i = new object();

//block statment
{
    int i; /// block scope

    i = 7;
    i++;
    console.writeline(i);

} ///end of i scope

{
    string i;

    i = "abc";

    console.writeline(i.tolower());
}

One D Array →

/ Array in C# , refrence Type
/ Object from Array class

/C Style
int Arr[5]

int[] Arr;
/Declaration for refrence of int Array 
/Zero Bytes have been alllocated in Heap

Arr = new int[5];

int[] Arr = new int[5] { 3, 4, 5, 6, 7 };

int[] Arr = new int[] { 3, 4, 5, 6, 7 };

int[] Arr = { 3, 4, 5, 6, 7 };

int[] Arr01 = { 1, 7, 5, 3, 8, 6, 4, 2 };

Array.Sort(Arr01);

Console.WriteLine($"Size {Arr01.Length} , Number of Dimensions {Arr01.Rank}");

int[] Arr02 = { 7, 8, 9 };

Console.WriteLine($"Arr01 {Arr01.GetHashCode()}");
Console.WriteLine($"Arr02 {Arr02.GetHashCode()}");

//Arr02 = Arr01;
///Same Object , Two References 
Console.WriteLine("Arr02 = Arr01");

Arr02 = (int[]) Arr01.Clone();
///int[] = (int[])object ;
///Derived = Base : Not Valid must use Explicit Casting
/// ref To Base = Derived : Valid
///Arr02 new Object with new(diff) identity but same state as Arr01
Console.WriteLine("After Clone");
Console.WriteLine($"Arr01 {Arr01.GetHashCode()}");
Console.WriteLine($"Arr02 {Arr02.GetHashCode()}");

for (int i = 0; i<Arr02.Length; i++)
    Console.Write($"{Arr02[i]} , ");
Console.WriteLine("");