Unboxing conversions

An unboxing conversion permits an explicit conversion from type object to any value-type or from any interface-type to any value-type that implements the interface-type. An unboxing operation consists of first checking that the object instance is a boxed value of the given value-type, and then copying the value out of the instance.
Referring to the imaginary boxing class described in the previous section, an unboxing conversion of an object box to a value-type T consists of executing the expression ((T_Box)box).value. [Example: Thus, the statements object box = 123; int i = (int)box; conceptually correspond to object box = new int_Box(123); int i = ((int_Box)box).value; end example]
For an unboxing conversion to a given value-type to succeed at run-time, the value of the source operand must be a reference to an object that was previously created by boxing a value of that value-type. If the source operand is null or a reference to an incompatible object, a System.InvalidCastException is thrown.