boxing and unboxing in c#

Boxing :-

  means converting value-type to reference-type.

Eg:

int I = 20;

string s = I.ToSting();

UnBoxing :- 
 means converting reference-type to value-type.

Eg:

int I = 20;

string s = I.ToString(); //Box the int

int J = Convert.ToInt32(s); //UnBox it back to an int.

Note: Performance Overheads due to boxing and unboxing as the boxing makes a copy of value type from stack and place it inside an object of type System.Object in the heap.

Value Type :-

As name suggest Value Type stores “value” directly.

For eg: 

//I and J are both of type int

I = 20;

J = I;

int is a value type, which means that the above statements will results in two locations in memory.

For each instance of value type separate memory is allocated.Stored in a Stack.

It Provides Quick Access, because of value located on stack.

 Reference Type : -

As name suggest Reference Type stores “reference” to the value.

For eg: 

Vector X, Y; //Object is defined. (No memory is allocated.)

X = new Vector(); //Memory is allocated to Object. //(new is responsible for allocating memory.)

X.value = 40; //Initialising value field in a vector class.

Y = X; //Both X and Y points to same memory location. //No memory is created for Y.

Console.writeline(Y.value); //displays 40, as both points to same memory

Y.value = 60;

Console.writeline(X.value); //displays 60.

Note: If a variable is reference it is possible to indicate that it does not refer to any object by setting its value to null;

Reference type are stored on Heap.

It provides comparatively slower access, as value located on heap.