string is a reference type as same as array..is it reference type?

Question

0.00/5 (No votes)

See more:

C#

class str
    {
        string s1 = "111";
        int[] ar1 = new int[1];

            public void add()
        {
         //   string s2 = s1;
            int[] ar2 = new int[1];
            ar2 = ar1;
            ar1[0] = 4;

            Console.WriteLine(ar1[0]);
            Console.WriteLine(ar2[0]);
            //s2 = "222";
                ar2[0] = 5;
            Console.WriteLine(ar1[0]);
            Console.WriteLine(ar2[0]);
        }
    }

in this example if we are giving the array value to second array,it is getting updated in first array also.Because it is reference type.But if we are doing in string,it is not working ....Why??

Posted 9-Apr-12 3:15am

samu4u

Add a Solution

3 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Ankur^\m/ · Accepted Answer · 2012-04-09T03:22:00

Solution 1

Because strings are immutable i.e they are read-only and their values cannot be modified. Every time you do an operation on a string, a new String Object is created.

For more information check the MSDN link - String Class[^] and scroll down to immutability.

Read the article and you will have a very clear picture about String objects.

Posted 9-Apr-12 3:22am

Ankur^\m/

Comments

VJ Reddy 9-Apr-12 9:41am

To the point. +5

Ankur^\m/ 9-Apr-12 9:55am

Thank you for your vote. Much appreciated!

Monjurul Habib 10-Apr-12 1:15am

5!

Not Active · Accepted Answer · 2012-04-09T03:23:00

Solution 2

String in .NET is a reference type but it is an immutable type, meaning that it can't be changed once it is created.

string s = string.Empty;
s = "Hello, World";
s = "Hello, " + "World";

In this case three new string objects will be created for s.

http://msdn.microsoft.com/en-us/library/362314fe.aspx[^]

Posted 9-Apr-12 3:23am

Not Active

Comments

VJ Reddy 9-Apr-12 9:40am

To the point. +5

Monjurul Habib 10-Apr-12 1:15am

5!

OriginalGriff · Accepted Answer · 2012-04-09T03:34:00

Solution 3

It's not simple to explain, but I'll try:
The first thing you need to know is that strings are immutable - when you declare a string (say "hello there") it cannot be changed, not even slightly. When you try, (Say by adding " Samu!") what happens is that the system adds the lengths of the two strings, allocates enough memory for the result, and copies both of then into it, returning the new string value - the original string is not changed in any way.
The other thing is that when you declare an array:

C#

int[] ar1 = new int[1];

You have done two operations:
1) You have decalared a variable called ar1 which can reference an array of ints.
2) You have constructed a new array of integers and assigned it's reference to ar1

What that means is that when you subsequently declare another variable:

C#

int[] ar2 = new int[1];
ar2 = ar1;

You first assign a reference to a new array to it, then overwrite that reference with the one that ar1 is referring to. ar1 and ar2 now both reference that same array in memory.

So when you change the array content via ar1 it affects the memory that ar2 is also refering to.

When you do "the same thing" with strings, it all happens the same:

C#

string s1 = "111";

Declares a string variable s1, and assigns it a reference to the memory holding "111".

C#

string s2 = s1;

Declares a string variable s2, and copies the reference from s1. The two variables now refer to the same string in memory: "111"

C#

s2 = "222";

Changes the reference of s2 to a new string in memory. It does not affect s1 in any way - s1 continues to refer to the memory holding "111"

Posted 9-Apr-12 3:34am

OriginalGriff

Updated 9-Apr-12 3:35am

v2

Comments

VJ Reddy 9-Apr-12 9:40am

Nice explanation. +5

samu4u 9-Apr-12 10:01am

so it will be just like an value type??
even 'int' is also doing the same thing,??
why they dint made string in that way??
so reference wont work over there... perfectly??right>??
thanks for the great explanation...

OriginalGriff 9-Apr-12 10:05am

No, a value type does not need the reference - it goes directly.
This is complex without pictures...
Do you understand what a pointer is?

samu4u 9-Apr-12 10:11am

it goes directly means to an address location, so that we never want to bother
about the location..
and int allocating memory directly..and the variable directly holding data rather than pointer type or reference type.
pointer concept is clear for me...

OriginalGriff 9-Apr-12 10:57am

Good!
A Reference is effectively a pointer: so when you declare a variable of a reference type, you are in fact declaring a pointer to memory-which-will-hold-the-data. When you declare a variable of a value type, you are declaring the actual memory which holds the value.
int is a value type, an array (of any form) is a reference type. So when you declare
int i = 6;
int[] a = new int[1];
you declare a value type called "i", which contains "6" and a reference type called "a" which holds a pointer to an array of value types.

If you re-read my explanation above, substituting "pointer" for "reference" you will hopefully get the idea!

samu4u 9-Apr-12 11:19am

thanks for the all answers,that is great, i got the clear picture....
one more thing,
Then why they(C# creators) made string as reference type.. why not as value type?

OriginalGriff 9-Apr-12 11:32am

Because it can be HUGE! A reference type can be 2GB - a value type is recommended to be no more than 16 bytes. Plus, of course, it couldn't easily be immutable! :laugh:

samu4u 9-Apr-12 11:39am

how the compiler is managing the reference type??
i am saying about memory locations(to store the values as well as retrieve the values)...how the compiler can understand these much location i have to refer for this string??

OriginalGriff 9-Apr-12 11:50am

That's part of why a reference isn't really a pointer - it "refers" to a piece of memory on the heap (or Large Object Heap, but ignore that for now) which can be moved at will by the garbage collector. The compiler knows if a object is value or reference (because value one always derive from ValueType, which reference types don't).
In fact the variable which holds the reference is technically a value type although what it refers to isn't ... but please ignore that, it'll make your head hurt. It does mine! :laugh:

Monjurul Habib 10-Apr-12 1:15am

5!