Boxing and unboxing enable value types to be treated as objects. Boxing a value type packages it inside an instance of the Object reference type. This allows the value type to be stored on the garbage collected heap. Unboxing extracts the value type from the object. In this example, the integer variable i is boxed and assigned to object o.

int i = 123;
object o = (object)i;  // boxing


The object o can then be unboxed and assigned to integer variable i:

o = 123;
i = (int)o;  // unboxing