modify a char in string

[Zeng]

Hello,

Is it true that in C# we can't modify directly a character in a string? I
can't find the method anywhere.

I would expect something like this should work,but it doesn't

string myStr = "blah';
myStr[ 3 ] = 'e';

Thanks in advance for your comment.

[rawCoder]

Cudnt find a direct method either but here is one of the indirect way

// Not Compiled-might have syntax errors
string str = "blah";
char[] arr = str.ToCharArray();
arr[3]='e';
str = new string( arr );

HTH
rawCoder

"Zeng" <Ze******@hotmail.com> wrote in message
news:%2******************@TK2MSFTNGP14.phx.gbl...

Hello,

Is it true that in C# we can't modify directly a character in a string? I
can't find the method anywhere.

I would expect something like this should work,but it doesn't

string myStr = "blah';
myStr[ 3 ] = 'e';

Thanks in advance for your comment.

[Morten Wennevik]

Hi Zeng,

It is correct, you cannot modify a string directly, but will need to
reassemble it, using SubString/Insert/Remove etc.

string myStr = "blah";
int pos = 3;
myStr = myStr.Substring(0, pos) + 'c' + myStr.Substring(++pos,
myStr.Length - pos);

Or you can do as rawCoder said and use ToArray and change the char[]

--
Happy Coding!
Morten Wennevik [C# MVP]

[RBischoff]

Hello Zeng,

you can't use the indexer on the string object to set chars, only read them.

Hope this helps,
RBischoff
-----------------------------------------
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http://www.mvps.org/vcfaq/ (C++ FAQ)
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http://msdn.microsoft.com/visualc/whidbey/ (CLI)

Z> Hello,
Z>
Z> Is it true that in C# we can't modify directly a character in a
Z> string? I can't find the method anywhere.
Z>
Z> I would expect something like this should work,but it doesn't
Z>
Z> string myStr = "blah';
Z> myStr[ 3 ] = 'e';
Z> Thanks in advance for your comment.
Z>

[Zeng]

Thanks, now that makes me really curious, does anyone know why it was
designed that way? There must be a reason for not allowing it.
"RBischoff" <ry****@NogmailSpAmPl.EaSe.com> wrote in message
news:28*********************@msnews.microsoft.com. ..

Hello Zeng,

you can't use the indexer on the string object to set chars, only read them.
Hope this helps,
RBischoff
-----------------------------------------
http://msdn.microsoft.com/visualc/ (VC++ HOME)
http://www.mvps.org/vcfaq/ (C++ FAQ)
http://www.winterdom.com/mcppfaq/ (MC++ FAQ)
http://msdn.microsoft.com/visualc/whidbey/ (CLI)

Z> Hello,
Z>
Z> Is it true that in C# we can't modify directly a character in a
Z> string? I can't find the method anywhere.
Z>
Z> I would expect something like this should work,but it doesn't
Z>
Z> string myStr = "blah';
Z> myStr[ 3 ] = 'e';
Z> Thanks in advance for your comment.
Z>

[Morten Wennevik]

Hi Zeng,

Strings are special because they are stored in an intern pool. All
strings in the pool are unique and each time you create a new string
object containing a string value that is already inside the pool you will
get a reference to the old string instead of creating a new string object.

Microsoft calls it an intern pool of unique strings. The documentation of
String.Intern explains it much better.

http://msdn.microsoft.com/library/en...nterntopic.asp
--
Happy Coding!
Morten Wennevik [C# MVP]

[Tom Porterfield]

Zeng wrote:

Thanks, now that makes me really curious, does anyone know why it was
designed that way? There must be a reason for not allowing it.

A string, once created, is immutable. That means that a string cannot be
changed, at least not easily or using the normal access methods. Any method
that looks like it is modifying a string is actually building a new string.
Among other things, this allows for memory effeciencies that couldn't be
achieved otherwise.

More info on strings in .NET can be found at
http://www.yoda.arachsys.com/csharp/strings.html.
--
Tom Porterfield

[jmd]

I think the following is another solution, but I have not tested it !

StringBuilder sb = new StringBuilder("blah");
sb[3] = 'e';
String myStr = sb.ToString();

Hope that helps.
jmd

"Zeng" <Ze******@hotmail.com> wrote in message
news:%2******************@TK2MSFTNGP14.phx.gbl...

Hello,

Is it true that in C# we can't modify directly a character in a string? I
can't find the method anywhere.

I would expect something like this should work,but it doesn't

string myStr = "blah';
myStr[ 3 ] = 'e';

Thanks in advance for your comment.

[Jon Skeet [C# MVP]]

Morten Wennevik <Mo************@hotmail.com> wrote:

Strings are special because they are stored in an intern pool. All
strings in the pool are unique and each time you create a new string
object containing a string value that is already inside the pool you will
get a reference to the old string instead of creating a new string object.

No you won't. Interning only happens when you tell it to, or when
you're using string literals. Here's proof of that:

using System;

class Test
{
static void Main()
{
string x = "1";
string y = new string(new char[]{'1'});
string z = string.Intern(y);

Console.WriteLine (object.ReferenceEquals(x,y));
Console.WriteLine (object.ReferenceEquals(y,z));
Console.WriteLine (object.ReferenceEquals(x,z));
}
}

x is guaranteed to be interned because it's a literal.
z is guaranteed to be the same as x because it's the interned value of
an equivalent string.
y is guaranteed to be different to both of them because it's a
reference to a *new* string, not an interned one.

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

[Morten Wennevik]

Ah, I didn't know that.
Would they be referencing the same internal string, since *new* isn't
specified?

On Fri, 8 Apr 2005 19:48:50 +0100, Jon Skeet [C# MVP] <sk***@pobox.com>
wrote:

Morten Wennevik <Mo************@hotmail.com> wrote:

Strings are special because they are stored in an intern pool. All
strings in the pool are unique and each time you create a new string
object containing a string value that is already inside the pool you
will
get a reference to the old string instead of creating a new string
object.

No you won't. Interning only happens when you tell it to, or when
you're using string literals. Here's proof of that:

using System;

class Test
{
static void Main()
{
string x = "1";
string y = new string(new char[]{'1'});
string z = string.Intern(y);
Console.WriteLine (object.ReferenceEquals(x,y));
Console.WriteLine (object.ReferenceEquals(y,z));
Console.WriteLine (object.ReferenceEquals(x,z));
}
}

x is guaranteed to be interned because it's a literal.
z is guaranteed to be the same as x because it's the interned value of
an equivalent string.
y is guaranteed to be different to both of them because it's a
reference to a *new* string, not an interned one.

--
Happy Coding!
Morten Wennevik [C# MVP]

[Jon Skeet [C# MVP]]

Morten Wennevik <Mo************@hotmail.com> wrote:

Ah, I didn't know that.

Would they be referencing the same internal string, since *new* isn't
specified?

Would what be referencing the same internal string?

(Note that when constructing y, I'm using the character literal '1' -
there isn't a string constructor which just takes another string.)

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

[Morten Wennevik]

Oh, hehe, I was writing a question regarding the two strings

string a = "Hello World";
string b = "Hello World";

.... but then I noticed you already mentioned this case.
I must have missed a line when deleting it :P
--
Happy Coding!
Morten Wennevik [C# MVP]