box and unbox in C#

Satya Prakash

14y2.8kVisual Basic .NET

describe box and unbox with example how it is stored in heap and stack.

3 Replies

Know the answer? Post it — somebody with the same question will find it here.

Prabhu Raja14y ago
For your Reference,

http://iamprabhuraja.wordpress.com/?s=boxing+and+unbox
Jignesh Trivedi14y ago
Hi,
Boxing is the process of converting a value type to the type object or to any interface type implemented by this value type. Boxing is used to store value types in the garbage-collected heap. Boxing is an implicit conversion of a value type to the type object or to any interface type implemented by this value type.
Unboxing is an explicit conversion from the type object to a value type or from an interface type to a value type that implements the interface.
int temp1 = 999;      // a value type
object tempObj = i;     // boxing
int temp2 = (int)tempObj;   // unboxing
please refer
http://www.codeproject.com/Articles/2225/Boxing-and-unboxing-in-C
http://www.csharphelp.com/2006/02/boxing-and-unboxing-c/
hope this will help you.
Vulpes14y ago
When you assign a value type to an object or interface variable, then it first needs to be converted to a reference type so that it can be stored on the heap using a process known as 'boxing'. A reference to the 'box' is then assigned to the object or interface variable.

When the value type needs to be retrieved, it needs to be 'unboxed' using a cast and then copied back to a variable of the value type. This variable will be stored on the stack (if it's a local variable or value parameter) or the heap otherwise (field, array element etc).

For example:

int i = 3;
object o = i; // 3 is boxed on heap
int j = (int)o; // 3 is unboxed and copied to the variable j
o = null;

The last line means that there are no longer any references to the box and so it can be garbage collected in due course.