What is boxing and unboxing?

Boxing permits any value type to be implicitly converted to type object or to any interface type implemented by value type. Boxing is a process in which object instances are created and copy values in to that instance. Unboxing is vice versa of boxing operation where the value is copied from the instance in to appropriate storage location. Below is sample code of boxing and unboxing where integer data type is converted in to object and then vice versa.
Dim x As Integer
Dim y As Object x = 10
' boxing process
y = x
' unboxing process
x = y (More...)

The example

class Test
{
static void Main() {
int i = 1;
object o = i; // boxing
int j = (int) o; // unboxing
}
}

An int value can be converted to object and back again to int.
This example shows both boxing and unboxing. When a variable of a value type needs to be converted to a reference type, an object box is allocated to hold the value, and the value is copied into the box.

Unboxing is just the opposite. When an object box is cast back to its original value type, the value is copied out of the box and into the appropriate storage location. (More...)