string immutability

[rb]

Hi

This is a sample code I am working on.

string a = "rb"
string b = a

Console.WriteLine(Object.ReferenceEquals(a,b))

In the above code, its printing true. I have a doubt on this output. When I say b = a, the system will create a new string called b and copy the value in a to b. Hence b and a should point to two new memory locations. Hence the output should be false, right

Can anybody clarify my doubt

Thanks

[Nicholas Paldino [.NET/C# MVP]]

rb,

This is not correct. Strings are reference types. When you declare b,
you are creating a new variable. When you assign a to b, then you are
copying the reference to a into the variable b. The references are copied,
not the actual object they point to. So, when you make the assignment, b is
pointing to the same thing a is.

Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"rb" <an*******@discussions.microsoft.com> wrote in message
news:33**********************************@microsof t.com...

Hi,

This is a sample code I am working on.

string a = "rb";
string b = a;

Console.WriteLine(Object.ReferenceEquals(a,b));

In the above code, its printing true. I have a doubt on this output. When I say b = a, the system will create a new string called b and copy the value
in a to b. Hence b and a should point to two new memory locations. Hence the
output should be false, right.
Can anybody clarify my doubt?

Thanks

[Jason Wang]

Immutability means when you MODIFY the string it will make a copy.

string b = a;

does not modify any value,

"rb" <an*******@discussions.microsoft.com> wrote in message
news:33**********************************@microsof t.com...

Hi,

This is a sample code I am working on.

string a = "rb";
string b = a;

Console.WriteLine(Object.ReferenceEquals(a,b));

In the above code, its printing true. I have a doubt on this output. When I say b = a, the system will create a new string called b and copy the value
in a to b. Hence b and a should point to two new memory locations. Hence the
output should be false, right.
Can anybody clarify my doubt?

Thanks

[Jon Skeet [C# MVP]]

Jason Wang <wa***@aegiscomgroup.com> wrote:

Immutability means when you MODIFY the string it will make a copy.

No it doesn't. It means you *can't* modify the string. No string
operations change it at all.

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,

"Jason Wang" <wa***@aegiscomgroup.com> wrote in message
news:%2****************@TK2MSFTNGP09.phx.gbl...

Immutability means when you MODIFY the string it will make a copy.

I think that a clarification is needed regarding immutable.

A class is said to be inmutable when the programmer assure that none of the
methods/properties call will change the instance over which the call is
made, instead a new instance of the same class is created and returned on
those call that would modify the instance.

Also take a look that AFAIK there is no way to mark a type as immutable and
make this enforced by the compiler, therefore you have to trust the
programmer of the type.

Just my 2 cts. :)

Cheers,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation