Technology Answer: String a value type part of generics constraint

If string is a value type, which I assume it is, why would the following declaration be legal:

struct Refsample<T> where T : class

RefSameple<string>; //why is it legal?

Taken from the C# in depth, page 75

From stackoverflow

System.String is a reference type, although it has some characteristics of a value type.
string is immutable reference type.

Are you trying to say?
```
struct Refsample<T> where T : class
```
struct itself is value type but it can contain reference type.

Value type variable stored in the memory stack, but reference type variable has a memory address that pointing to the heap.

e.g.
```
struct Refsample<T> where T : class
{
   // stored in the stack as well.
   public int Age; 

   // memory address pointing to the heap stored in the stack, 
   // but the actual object is stored in the heap.
   public string Name；
   // same as string above if T was reference type;
   // otherwise, if value type, same as Age above.
   public T SomeThing; 
}
```
Jon Skeet : A value type value is only stored on the stack when it's (directly or indirectly) part of a local variable. See http://pobox.com/~skeet/csharp/memory.html
String is really a reference type that acts like a value type. That's why you can test against null for a string and you can't for int, bool, etc. Well, you can, but you will just get the default value 0, false, etc.
System.String is a reference type not a value type.

Technology Answer