Boxing and Unboxing

Question

its a type and reference casting

Dipen Lama · Answer

.NET defines two categories of data types - value type and reference type while value type are stored in stack reference type are stored in .Net managed heap you may occasionally need to convert a variable of one type as a variable of the other type. .Net provides a very simple mechanism boxing and unboxing  to convert a value type to a reference type and vica-versa. Let us have variable of type int : int age = 30; If during the course of your application you wish to represent this value type as a reference type you would “box” the value as follows: object objAge = age; Boxing can be formally defined as the process of explicitly converting a value type into a corresponding reference type by storing the variable in a System.Object . When you box a value the CLR allocates a new object on the heap and copies the value type’s value (in this case 30) into that instance. What is returned to you is a reference to the newly allocated object. Using this technique .NET developers have no need to make use of a set of wrapper classes used to temporarily treat stack data as heap-allocated objects. The opposite operation is also permitted through unboxing . Unboxing is the process of converting the value held in the object reference back into a corresponding value type on the stack. The unboxing operation begins by verifying that the receiving data type is equivalent to the boxed type and if so it copies the value back into a local stack-based variable. For example the following unboxing operation works successfully given that the underlying type of the objAge is indeed a integer : int intAge = (int)objAge;