By using this site, you agree to our updated Privacy Policy and our Terms of Use. Manage your Cookies Settings.
424,946 Members | 773 Online
Bytes IT Community
+ Ask a Question
Need help? Post your question and get tips & solutions from a community of 424,946 IT Pros & Developers. It's quick & easy.

How are "const" literal Strings stored?

P: n/a
Back in the old Visual C++ days, it was always important to define constant
strings only once so that they wouldn't be stored over and over again in
memory. Has .NET resolved this issue? Consider these two code snippets:

Example A
========
const String hey="hey";
MessageBox.Show(hey);
MessageBox.Show(hey);
MessageBox.Show(hey);

Example B
========
MessageBox.Show("hey");
MessageBox.Show("hey");
MessageBox.Show("hey");

Does Example A make more efficient use of memory since "hey" is only stored
once in memory?... or is Example B just as efficient because the compiler is
smart enough to realize that "hey" is the *same* constant literal string
that is referenced three times in a row?

Sincerely,

Michael Jackson's Nose
Jul 21 '05 #1
Share this Question
Share on Google+
5 Replies


P: n/a
Lecture,

The latter is true. The compiler is smart enough to know that "hey" is
the same literal string, and will store it in the assembly once, referencing
it once (at least, it should).

The runtime is even smart enough to know that if you have "hey" in one
assembly (as a literal) and "hey" in another assembly, only one instance
will be created per app domain.

Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com
"Lecture Snoddddgrass" <ma***@hamburg.fry> wrote in message
news:eB**************@TK2MSFTNGP12.phx.gbl...
Back in the old Visual C++ days, it was always important to define constant strings only once so that they wouldn't be stored over and over again in
memory. Has .NET resolved this issue? Consider these two code snippets:

Example A
========
const String hey="hey";
MessageBox.Show(hey);
MessageBox.Show(hey);
MessageBox.Show(hey);

Example B
========
MessageBox.Show("hey");
MessageBox.Show("hey");
MessageBox.Show("hey");

Does Example A make more efficient use of memory since "hey" is only stored once in memory?... or is Example B just as efficient because the compiler is smart enough to realize that "hey" is the *same* constant literal string
that is referenced three times in a row?

Sincerely,

Michael Jackson's Nose

Jul 21 '05 #2

P: n/a
Lecture Snoddddgrass <ma***@hamburg.fry> wrote:
Back in the old Visual C++ days, it was always important to define constant
strings only once so that they wouldn't be stored over and over again in
memory. Has .NET resolved this issue? Consider these two code snippets:

Example A
========
const String hey="hey";
MessageBox.Show(hey);
MessageBox.Show(hey);
MessageBox.Show(hey);

Example B
========
MessageBox.Show("hey");
MessageBox.Show("hey");
MessageBox.Show("hey");

Does Example A make more efficient use of memory since "hey" is only stored
once in memory?... or is Example B just as efficient because the compiler is
smart enough to realize that "hey" is the *same* constant literal string
that is referenced three times in a row?


Example B is just as efficient - string literals are interned.

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too
Jul 21 '05 #3

P: n/a
Is it not also true that if you do somethign like:

a = "hello";
b = "hello";

That the "hello" will only be stored once overall? When, later in the
program you do a

b += "world";

Only then does the "hello" string get copied somewhere else as it is now a
different string from the original?

I believe I read that somewhere but do not remember for a fact where.

--
gabriel
Jul 21 '05 #4

P: n/a
Strings are pointers to a string table somewhere in memory. In your first
example a and b both point to the same string table entry so "hello" is stored
once. If you concat "world" to the string, you create a brand new string, in
this
case "helloworld" that is then placed in said string table. a still points to
"hello"
while b points to this new string.

This points out why string concatenation is bad, at least at run-time where the
compiler can't optimize it out, because you can wind up with *intermediate*
strings
in the string table that you never wind up using.
--
Justin Rogers
DigiTec Web Consultants, LLC.
Blog: http://weblogs.asp.net/justin_rogers

"gabriel" <no@no--spam.com> wrote in message
news:6d**************************@msgid.meganewsse rvers.com...
Is it not also true that if you do somethign like:

a = "hello";
b = "hello";

That the "hello" will only be stored once overall? When, later in the
program you do a

b += "world";

Only then does the "hello" string get copied somewhere else as it is now a
different string from the original?

I believe I read that somewhere but do not remember for a fact where.

--
gabriel

Jul 21 '05 #5

P: n/a
100
Hi Lecture,

Both are equivalent. They produce the same code. The only difference is that
when you declare a string as a constant you make the code easier to maintain
and can export those strings for using by other assemblies. However when the
compiler compiles the code it reads the string literal from the assembly
metadata and uses the string as if it was written as a string in the place
of using.

So,
const String hey="hey";
MessageBox.Show(hey);
and
MessageBox.Show("hey");

are exactly the same

HTH
B\rgds
100

"Lecture Snoddddgrass" <ma***@hamburg.fry> wrote in message
news:eB**************@TK2MSFTNGP12.phx.gbl...
Back in the old Visual C++ days, it was always important to define constant strings only once so that they wouldn't be stored over and over again in
memory. Has .NET resolved this issue? Consider these two code snippets:

Example A
========
const String hey="hey";
MessageBox.Show(hey);
MessageBox.Show(hey);
MessageBox.Show(hey);

Example B
========
MessageBox.Show("hey");
MessageBox.Show("hey");
MessageBox.Show("hey");

Does Example A make more efficient use of memory since "hey" is only stored once in memory?... or is Example B just as efficient because the compiler is smart enough to realize that "hey" is the *same* constant literal string
that is referenced three times in a row?

Sincerely,

Michael Jackson's Nose

Jul 21 '05 #6

This discussion thread is closed

Replies have been disabled for this discussion.