The following table lists the instruction's hexadecimal and Microsoft Intermediate Language (MSIL) assembly format, along with a brief reference summary:

79 < T >	unbox valType	Extracts the value type data from obj, its boxed representation.

The stack transitional behavior, in sequential order, is:

[The 'ordered' type of list has not been implemented in the ECMA stylesheet.]

A value type has two separate representations within the Common Language Infrastructure (CLI):

• A 'raw' form used when a value type is embedded within another object.

• A 'boxed' form, where the data in the value type is wrapped (boxed) into an object so it can exist as an independent entity.

The unbox instruction converts the object reference (type O), the boxed representation of a value type, to a value type pointer (a managed pointer, type &), its unboxed form. The supplied value type (valType) is a metadata token indicating the type of value type contained within the boxed object.

Unlike OpCodes.Box, which is required to make a copy of a value type for use in the object, unbox is not required to copy the value type from the object. Typically it simply computes the address of the value type that is already present inside of the boxed object.

InvalidCastException is thrown if the object is not boxed as valType.

NullReferenceException is thrown if the object reference is a null reference.

TypeLoadException is thrown if the value type valType cannot be found. This is typically detected when Microsoft Intermediate Language (MSIL) instructions are converted to native code, rather than at runtime.

The following ILGenerator.Emit(OpCode) method overload can use the unbox opcode:

• ILGenerator.Emit(OpCode, Type)

Namespace: System.Reflection.Emit
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0, 4.0.0.0