string problem

[Mosquito Man]

string s("0101");

I can't change it into s=1101
by

s[0]='1';

because string.this[i] is read-only, no assignment is allowed :-(

thank you for your help

[Peter Duniho]

Re: string problem

"Mosquito Man" <modermjersay@y ahoo.comwrote in message
news:1163836241 .928244.210640@ k70g2000cwa.goo glegroups.com.. .

string s("0101");
>
I can't change it into s=1101
by
>
s[0]='1';
>
because string.this[i] is read-only, no assignment is allowed :-(

Perhaps the StringBuilder class is more suitable for your needs.

[Dave Sexton]

Re: string problem

Hi,

System.String is immutable. A better choice would be to use a StringBuilder:

StringBuilder s = new StringBuilder(" 0101");
s[0] = '1';

--
Dave Sexton

"Mosquito Man" <modermjersay@y ahoo.comwrote in message
news:1163836241 .928244.210640@ k70g2000cwa.goo glegroups.com.. .

string s("0101");
>
I can't change it into s=1101
by
>
s[0]='1';
>
because string.this[i] is read-only, no assignment is allowed :-(
>
thank you for your help
>

[Truong Hong Thi]

Re: string problem

Hi,

If you want to change the string that way, you'd better use
StringBuilder class.

string s = "0101";
StringBuilder builder = new StringBuilder(s );
builder [0] = '1';
builder [3] = '0';
s = builder.ToStrin g();

An alternative is use String.ToCharAr ray. You than can set each char to
whatever you want, then create a new string, past the array to string
constructor.

string s = "0101";
char[] chars = s.ToCharArray() ;
chars[0] = '1';
chars[3] = '0';
s = new String(chars);

Thi

http://thith.blogspot.com

Mosquito Man wrote:

string s("0101");
>
I can't change it into s=1101
by
>
s[0]='1';
>
because string.this[i] is read-only, no assignment is allowed :-(
>
thank you for your help

[Mark R. Dawson]

RE: string problem

Hi,
strings are immutable, so you cannot change the contents of a string once
it has been defined. If you want to change values you are going to have to
use some combination of .SubString .Replace etc to replace individual values.

HTH
Mark.
--

http://www.markdawson.org

"Mosquito Man" wrote:

string s("0101");
>
I can't change it into s=1101
by
>
s[0]='1';
>
because string.this[i] is read-only, no assignment is allowed :-(
>
thank you for your help
>
>

[Jon Shemitz]

Re: string problem

Truong Hong Thi wrote:

If you want to change the string that way, you'd better use
StringBuilder class.

An alternative is use String.ToCharAr ray. You than can set each char to
whatever you want, then create a new string, past the array to string
constructor.
>
string s = "0101";
char[] chars = s.ToCharArray() ;
chars[0] = '1';
chars[3] = '0';
s = new String(chars);

Of course, this latter is exactly what the StringBuilder class is
doing. All you gain by taking the manual approach is saving a very few
cycles by not creating a StringBuilder instance ... at the cost of
bigger, more complex source code that is harder to maintain.

--

https://www.midnightbeach.com/.net

What you need to know.

[rossum]

Re: string problem

On 17 Nov 2006 23:50:42 -0800, "Mosquito Man" <modermjersay@y ahoo.com>
wrote:

>string s("0101");
>
>I can't change it into s=1101
>by
>
>s[0]='1';
>
>because string.this[i] is read-only, no assignment is allowed :-(
>
>thank you for your help

Others have pointed you to the StringBuilder class, which is probably
the solution you are looking for.

An alternative is to drop into unsafe code and use pointers which do
allow you to change otherwise "immutable" strings:

unsafe void OverwriteChar(s tring text, int pos, char newChar) {
fixed (char* cPointer = text) {
cPointer[pos] = newChar;
}
}

I use this technique to overwrite security sensitive strings before
releasing them for garbage collection.

rossum

[Willy Denoyette [MVP]]

Re: string problem

"rossum" <rossum48@coldm ail.comwrote in message
news:8bsul2pj9v 4hnuf8e19o1gn37 bga0b6jqm@4ax.c om...

On 17 Nov 2006 23:50:42 -0800, "Mosquito Man" <modermjersay@y ahoo.com>
wrote:
>

>>string s("0101");
>>
>>I can't change it into s=1101
>>by
>>
>>s[0]='1';
>>
>>because string.this[i] is read-only, no assignment is allowed :-(
>>
>>thank you for your help

Others have pointed you to the StringBuilder class, which is probably
the solution you are looking for.
>
An alternative is to drop into unsafe code and use pointers which do
allow you to change otherwise "immutable" strings:
>
unsafe void OverwriteChar(s tring text, int pos, char newChar) {
fixed (char* cPointer = text) {
cPointer[pos] = newChar;
}
}
>
I use this technique to overwrite security sensitive strings before
releasing them for garbage collection.
>
rossum
>

V2 of the framework provides a SecureString (System.Securit y) which has the advantage to be
encrypted when live and deleted from memory when detached, no need for unsafe code.
Willy.

[rossum]

Re: string problem

On Sat, 18 Nov 2006 22:11:43 +0100, "Willy Denoyette [MVP]"
<willy.denoyett e@telenet.bewro te:

>"rossum" <rossum48@coldm ail.comwrote in message
>news:8bsul2pj9 v4hnuf8e19o1gn3 7bga0b6jqm@4ax. com...

>On 17 Nov 2006 23:50:42 -0800, "Mosquito Man" <modermjersay@y ahoo.com>
>wrote:
>>

>>>string s("0101");
>>>
>>>I can't change it into s=1101
>>>by
>>>
>>>s[0]='1';
>>>
>>>because string.this[i] is read-only, no assignment is allowed :-(
>>>
>>>thank you for your help

>Others have pointed you to the StringBuilder class, which is probably
>the solution you are looking for.
>>
>An alternative is to drop into unsafe code and use pointers which do
>allow you to change otherwise "immutable" strings:
>>
> unsafe void OverwriteChar(s tring text, int pos, char newChar) {
> fixed (char* cPointer = text) {
>cPointer[pos] = newChar;
> }
> }
>>
>I use this technique to overwrite security sensitive strings before
>releasing them for garbage collection.
>>
>rossum
>>

>
>
>V2 of the framework provides a SecureString (System.Securit y) which has the advantage to be
>encrypted when live and deleted from memory when detached, no need for unsafe code.
>Willy.

Thanks for that, I used the technique in V1 and haven't needed it
since the move to V2.

rossum

[Jon Skeet [C# MVP]]

Re: string problem

rossum <rossum48@coldm ail.comwrote:

On 17 Nov 2006 23:50:42 -0800, "Mosquito Man" <modermjersay@y ahoo.com>
wrote:
>

string s("0101");

I can't change it into s=1101
by

s[0]='1';

because string.this[i] is read-only, no assignment is allowed :-(

thank you for your help

Others have pointed you to the StringBuilder class, which is probably
the solution you are looking for.
>
An alternative is to drop into unsafe code and use pointers which do
allow you to change otherwise "immutable" strings:
>
unsafe void OverwriteChar(s tring text, int pos, char newChar) {
fixed (char* cPointer = text) {
cPointer[pos] = newChar;
}
}
>
I use this technique to overwrite security sensitive strings before
releasing them for garbage collection.

Note that that can produce *very* disturbing results - in this case, if
the literal "0101" were changed, *all* string literals in the code
which should be "0101" would then be "1101".

--
Jon Skeet - <skeet@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too