Does String.Replace always recreate a new string object?

[Sin Jeong-hun]

If I use something like this,

string html = "<h1>C# is great</h1>";
Console.WriteLi ne(html.Replace ("&lt;","<").Re place("&gt;","> "));

Does this recreate new string objects two times, even though it has
nothing to replace, and it is OK to return the same string object?

I know, regular expression is a more delicate way to do this, but it
always is kind of too complicated to me.
Thank you.

[Hilton]

Re: Does String.Replace always recreate a new string object?


"Sin Jeong-hun" <typingcat@gmai l.comwrote in message
news:656870e0-4f9a-4ace-867a-b1a12520cb25@j2 8g2000hsj.googl egroups.com...

If I use something like this,
>
string html = "<h1>C# is great</h1>";
Console.WriteLi ne(html.Replace ("&lt;","<").Re place("&gt;","> "));
>
Does this recreate new string objects two times, even though it has
nothing to replace, and it is OK to return the same string object?

No, Replace (string, string) does not always create a new string.

Hilton

[Marc Gravell]

Re: Does String.Replace always recreate a new string object?

This returns true because the CLR uses string interning to optimize

string handling.

Actually it seems to work even if the strings aren't interned, suggesting it
is instead a "I didn't update anything, return the original reference"
optimisation; since it is an internal-call, it is hard to check...

Anyways, s1 and s2 come out as ref-equals, even though it isn't interned.

Marc

string s0 = "foobar"; // expect this to be interned
Console.WriteLi ne("s0: {0}", s0);
Console.WriteLi ne("s0 interned: {0}", (string.IsInter ned(s0) !=
null));
string s1 = new string('a',5); // don't expect this to be
interned
Console.WriteLi ne("s1: {0}", s1);
Console.WriteLi ne("s1 interned: {0}", (string.IsInter ned(s1) !=
null));
string s2 = s1.Replace("b", "c");
Console.WriteLi ne("s2: {0}", s1);
Console.WriteLi ne("ref-equals: {0}", object.Referenc eEquals(s1,
s2));
Console.WriteLi ne("s1 interned: {0}", (string.IsInter ned(s1) !=
null));
Console.WriteLi ne("s2 interned: {0}", (string.IsInter ned(s2) !=
null));

[Marc Gravell]

Re: Does String.Replace always recreate a new string object?

(I'm going to have to find a faster nntp feed ;-p)