checks to ensure they are correct. For an explicit reference conversion to succeed at run-time, the value of the source operand must be null, or the actual type of the object referenced by the source operand must be a type that can be converted to the destination type by an implicit reference conversion (?3.1.4). If an explicit reference conversion fails, a System.InvalidCastException is thrown. Reference conversions, implicit or explicit, never change the referential identity of the object being converted. [Note: In other words, while a reference conversion may change the type of the reference, it never changes the type or value of the object being referred to. end note] 13.2.4 Unboxing conversions An unboxing conversion permits an explicit conversion from type object or System.ValueType 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. A struct can be unboxed from the type System.ValueType, since that is a base class for all structs (?8.3.2). Unboxing conversions are described further in ?1.3.2.
13.2.5 User-defined explicit conversions A user-defined explicit conversion consists of an optional standard explicit conversion, followed by execution of a user-defined implicit or explicit conversion operator, followed by another optional standard explicit conversion. The exact rules for evaluating user-defined conversions are described in ?3.4.4.
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