CHAPTER 18 ■ CONVERSIONS

The Boxing Conversions

Figure 18-24 shows the boxing conversions. Any value type ValueTypeS can be implicitly converted to any of types object, System.ValueType, or InterfaceT, if ValueTypeS implements InterfaceT.

Figure 18-24. Boxing is the implicit conversion of value types to reference types.

Unboxing Conversions

Unboxing is the process of converting a boxed object back to its value type.

•Unboxing is an explicit conversion.

•The system performs the following steps when unboxing a value to ValueTypeT:

—It checks that the object being unboxed is actually a boxed value of type ValueTypeT .

—It copies the value of the object to the variable.

For example, the following code shows an example of unboxing a value.

•Value type variable i is boxed and assigned to reference type variable oi.

•Variable oi is then unboxed, and its value is assigned to value type variable j.

static void Main()

{

int i = 10;

Box i and assign its reference to oi.

}

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CHAPTER 18 ■ CONVERSIONS

This code produces the following output:

i: 10, oi: 10, j: 10

Attempting to unbox a value to a type other than the original type raises an InvalidCastException exception.

The Unboxing Conversions

Figure 18-25 shows the unboxing conversions.

Figure 18-25. The unboxing conversions

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