If string is reference type, why pass by reference is not happening?

Question

I had read an article http://www.albahari.com/valuevsreftypes.aspx

As per this, int is a value type and form is an example of reference type.

Point myPoint = new Point (0, 0);      // a new value-type variable
Form myForm = new Form();              // a new reference-type variable
string mystringval="test";
Test (myPoint, myForm);                // Test is a method defined below

void Test (Point p, Form f)
{
      p.X = 100;                       // No effect on MyPoint since p is a copy
      f.Text = "Hello, World!";        // This will change myForm’s caption since
                                       // myForm and f point to the same object
      f = null;                        // No effect on myForm
}

So instead of form variable myform, if I pass a string value to the function test, will it also change the original value which I already declared outside?

Also what is the benefit of keeping the string as reference type, if, anyhow the value will be saved in stack and only the reference will be stored in heap?

Answer 1

if i pass a string value to the function test, will it also change the original value which i already declared outside?

No, neither did the value of myForm change, the myForm variable still points/refers to the same Form object (the object created via new Form()).

In your Test method, when you called:

f.Text = "Hello, World!";

You did not change the variable f, you changed f.Text which is a different.

In other words, you are changing a property on the object that both f and myForm refer to. But still f and myForm refer to the same original object.

Note that when you changed f to null, the variable myForm did not change. Now, f refers to nothing, but the myForm variable still refers to the original object.

If you want to change the original myForm variable (make it point/refer to another Form object) or mystringval (make it refer to another string) then pass them to the test method by reference like this:

void Test (Point p, ref Form f)
{
    ...
}

void Test (Point p, ref string s)
{
    ...
}