The difference between boxing and unboxing

Boxing and unboxing is an important concept in C#’s type system. With Boxing and unboxing you can link between value types and reference types by allowing any value of a value type to be converted to and from type object. When you 'box' a value type, it wraps the value inside a System.Object and stores it on the managed heap. Unboxing does the reverese, it extracts the value type from the object.

The following code snippet demonstrates boxing and unboxing:

public static void Main() {
   Int32 v = 5;    // Create an unboxed value type variable
   Object o = v;   // o refers to a boxed version of v
   v = 10;        // Changes the unboxed value to 10

   Console.WriteLine(v + ", " + (Int32) o);    // Displays "10, 5"
}

Here is a more simple example:

Boxing:

int i = 5;
object o = i;  // boxing

Unboxing:

o = 5;
i = (int)o;  // unboxing