why string is a reference type?

Question

We know that string is a reference type , so we have

string s="God is great!";

but on the same note if i declare class say Employee which is a reference type so why below piece of code does not work ?

Employee e = "Saurabh";

2- How do we actually determine if a type is a reference type or value type?

Answer 1

The "code below" doesnt work because you are trying to set e to a string, when e is of type Employee. Type safety prevents this.

Answer 2

Reference types are not assignable unless they are of the exact same type (this is known as type safety). The first example works because you are assigning a string literal to a variable of the type System.String. The second example does not work because you are assigning a string literal to a variable of the type Employee. The types must match or be assignable from right to left for value assignment to work.

Answer 3

Employee e = "Saurabh";

will not work simply because they are of different types.

Answer 4

That code would work if you had an implicit conversion from a string to an Employee. Basically a string literal is of type string - i.e. its value is a string reference (and an interned one at that). You can only assign a value of one type to a variable of another type if there's a conversion between the two types - either user-defined or built in. In this case, there's no conversion from string to Employee, hence the error.

Contrary to some other answers, the types don't have to be the same - for example, this is fine:

object x = "string literal";

That's fine because there's an implicit reference conversion from string to object. Likewise you can write:

XNamespace ns = "some namespace";

because there's an implicit conversion from string to XNamespace.

To answer your second question: to see if a type in .NET is a value type or a reference type... struct and enum types are value types; everything else (class, delegate, interface, array) is a reference type. That's excluding pointer types, which are a bit different :)

Answer 5

Because they're not the same type, if you define a TypeConverter then that would work.

http://msdn.microsoft.com/en-us/library/system.componentmodel.typeconverter.aspx

Answer 6

object x;

x = new Employee();

x = "Hello World!";

Answer 7

Here one more basic question

Class A {

public virtual void Method1(){}

public void Method2() {

Method1(); }

}

class B:A { public override void Method1() { } }

Class main

{

A obk = new B(); obk.Method2(); }

now tell me which function gets called ? sorry for the typos.

Answer 8

To determine whether a type is a reference type or not...

    string s = "foo";
    bool sIsRef = !s.GetType().IsValueType;  // true

    int i = 100;
    bool iIsRef = !i.GetType().IsValueType;  // false