Value Type and Reference Type Storage

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.NET3.5

A value type is stored in a stack
A reference type is allocated memory on a heap.

A reference type has value types, eg class can have basic int properties or structs and structs can have a class object.
Then how does the class/struct get stored in the memory.
Does the struct gets memory allocation in stack or heap and where is the class contained in the struct goes.
Similarly a class having the value type is stored in heap however the where are the members of the class are stored like int variables etc.

Posted 11-Feb-13 17:22pm

Sakshi Smriti

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Sergey Alexandrovich Kryukov 11-Feb-13 23:42pm

Who told you so? :-)
—SA

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SruthiR · Accepted Answer · 2013-02-11T17:35:00

Thats wrong. Not all value types are saved on the stack.

Many developers believe that reference types are stored on the heap while value types are always stored on the stack – this is not entirely true.

First it’s more of an implementation detail of the actual runtime and not a language requirement but more importantly it’s not possible – consider a class (reference type) which has a integer member (value type), the class is stored on the heap and so are it’s members including the value type since its data is copied “by-value”.

C#

class MyClass
{
    // stored in heap
    int a = 5;
}

SruthiR · Accepted Answer · 2013-02-11T17:41:00

Solution 2

You can read Eric Lippert's post - http://blogs.msdn.com/b/ericlippert/archive/2009/04/27/the-stack-is-an-implementation-detail.aspx[^]

Don't forget to mark it as answer if it helped you. Good luck!!

Posted 11-Feb-13 17:41pm

SruthiR

Sergey Alexandrovich Kryukov · Accepted Answer · 2013-02-11T17:42:00

No. This is not that simple. Values type objects are not stored just on stack. It depends on where they are used. They are stored on 1) stack; 2) memory reserved for static members, 3) on heap, when are used as a members of reference types (classes).

When a class is instantiated, it also not so simple. All reference variables/members take some place in memory. Suppose you have a local variable of a reference type. It is allocated on stack. Then you instantiate it, or assign already instantiated variable to it. Nothing happens to the reference itself — it remains on stack. But the value of the reference starts referencing some memory on stack. In second case, when you assign an already instantiated reference, you got two references referencing the same object on heap.

Consider references as "managed pointers" (C++/CLI terminology). They are not "real" pointers (this is not a place to discuss how managed system works in detail), but they are like pointers in terms of storage: the pointer "points" to some object (in case of .NET this is always the managed heap; I don't discuss unsafe pointers here which use the pointer syntax), but the pointer itself takes up some memory. Where? Again: on heap, on stack, in the "static" memory area.

In all cases, you should consider all the chain: what contains what.

—SA

Value Type and Reference Type Storage

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