How do you store an int or other "C# value types" on the heap (with C#)?

Question

I'm engaged in educating myself about C# via Troelsen's Pro C# book.

I'm familiar with the stack and heap and how C# stores these sorts of things. In C++, whenever we use new we receive a pointer to something on the heap. However, in C# the behavior of new seems different to me:

• when used with value types like an int, using new seems to merely call the int default constructor yet the value of such an int would still be stored on the stack

I understand that all objects/structs and such are stored on the heap, regardless of whether or not new is used.

So my question is: how can I instantiate an int on the heap? (And does this have something to do with 'boxing'?)

Answer 1

You can box any value type to System.Object type so it will be stored on the managed heap:

int number = 1;
object locatedOnTheHeap = number;

An other question is why you need this.

This is a classic example from the must-know MSDN paper: Boxing and Unboxing (C# Programming Guide)

When the CLR boxes a value type, it wraps the value inside a System.Object and stores it on the managed heap. 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. Boxing a value type allocates an object instance on the heap and copies the value into the new object.

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I understand that all objects/structs and such are stored on the heap

BTW, IIRC sometimes JIT optimizes code so value type objects like of type like int are stored in the CPU registers rather than stack.

Answer 2

I do not know why you would want to do this, however, in theory you could indeed box your value. You would do this by boxing the int into an object (which is a reference type and will be placed on the stack:

object IAmARefSoIWillBeOnHeap = (object)1;

*As sll stated, you do not need the (object) as it will be an implicit cast. This is here merely for academic reasons, to show what is happening.

Here is a good article about reference versus value types, which is the difference of the heap versus the stack