string.Trim() Behavior

[Jonathan Wood]

According to the intellisense help, string.Trim() "Removes all occurances or
white space characters from the beginning and end of this instance."

However, the follow code does not appear to modify s.

s.Trim('\r');

While the follow code DOES modify s.

s = s.Trim(\r');

I understand that the help text quoted above is for the version of this
method that takes no arguments. But I would assume that variations of Trim
work the same fundamental way.

If this is modifying this instance, why do I only get the effect if I assign
the result?

Thanks.

--
Jonathan Wood
SoftCircuits Programming
http://www.softcircuits.com

[Ryan Liu]

Hi Jonathan,

string value is immutable.

A String is called immutable because its value cannot be modified once it
has been created. Methods that appear to modify a String actually return a
new String containing the modification. If it is necessary to modify the
actual contents of a string-like object, use the System.Text.Str ingBuilder
class.

(See:
ms-help://MS.NETFramework SDKv1.1/cpref/html/frlrfsystemstri ngclasstopic.ht m)

so Trim method always return you a NEW string.

HTH,
Ryan
"Jonathan Wood" <jw***@softcirc uits.comдÈëÓʼ þ
news:Oz******** *****@TK2MSFTNG P04.phx.gbl...

According to the intellisense help, string.Trim() "Removes all occurances

or

white space characters from the beginning and end of this instance."

However, the follow code does not appear to modify s.

s.Trim('\r');

While the follow code DOES modify s.

s = s.Trim(\r');

I understand that the help text quoted above is for the version of this
method that takes no arguments. But I would assume that variations of Trim
work the same fundamental way.

If this is modifying this instance, why do I only get the effect if I

assign

the result?

Thanks.

--
Jonathan Wood
SoftCircuits Programming
http://www.softcircuits.com

[jeremiah johnson]

my GUESS is that it was written that way on purpose. Also, strings are
immutable. reassigning back to itself actually causes a new string
object to be created, thus it works.

but again, i'm guessing.

Jonathan Wood wrote:

According to the intellisense help, string.Trim() "Removes all occurances or
white space characters from the beginning and end of this instance."

However, the follow code does not appear to modify s.

s.Trim('\r');

While the follow code DOES modify s.

s = s.Trim(\r');

I understand that the help text quoted above is for the version of this
method that takes no arguments. But I would assume that variations of Trim
work the same fundamental way.

If this is modifying this instance, why do I only get the effect if I assign
the result?

Thanks.

--
Jonathan Wood
SoftCircuits Programming
http://www.softcircuits.com

--
jeremiah();

[Tom Spink]

Jonathan Wood wrote:

According to the intellisense help, string.Trim() "Removes all occurances
or white space characters from the beginning and end of this instance."

However, the follow code does not appear to modify s.

s.Trim('\r');

While the follow code DOES modify s.

s = s.Trim(\r');

I understand that the help text quoted above is for the version of this
method that takes no arguments. But I would assume that variations of Trim
work the same fundamental way.

If this is modifying this instance, why do I only get the effect if I
assign the result?

Thanks.

--
Jonathan Wood
SoftCircuits Programming
http://www.softcircuits.com

Hi Jonathan,

While a string object is a reference object, it is classed as immutable,
meaning that you cannot modify it's value once it's created. The 'Trim'
method, and indeed all other string methods cannot alter the contents of
the string object, so they *must* return a new string object.

The line:
s = s.Trim('\r');

Does not modify the object, it reassigns 's' to the newly created string
object, that results from trimming '\r' from the current value of 's'.

--
Hope this helps,
Tom Spink

Google first, ask later.

[Jonathan Wood]

Ryan,

string value is immutable.

A String is called immutable because its value cannot be modified once it
has been created. Methods that appear to modify a String actually return a
new String containing the modification. If it is necessary to modify the
actual contents of a string-like object, use the System.Text.Str ingBuilder
class.

(See:
ms-help://MS.NETFramework SDKv1.1/cpref/html/frlrfsystemstri ngclasstopic.ht m)

so Trim method always return you a NEW string.

Thanks for the explanation. I can see it working that way but found the
intellisense help misleading. It seems to suggest it does exactly what you
are saying (and I can see) it does not do. But the explanation above helps
point me in the right direction.

Thanks.

--
Jonathan Wood
SoftCircuits Programming
http://www.softcircuits.com

[Jonathan Wood]

Tom,

While a string object is a reference object, it is classed as immutable,
meaning that you cannot modify it's value once it's created. The 'Trim'
method, and indeed all other string methods cannot alter the contents of
the string object, so they *must* return a new string object.

The line:
s = s.Trim('\r');

Does not modify the object, it reassigns 's' to the newly created string
object, that results from trimming '\r' from the current value of 's'.

Right, I understand that. I'm a long time programmer trying to make the jump
to .NET.

I guess I'd forgot that string types cannot be modified. I just found the
intellisense help completely misleading.

Thanks for getting me back up on the straight and narrow.

--
Jonathan Wood
SoftCircuits Programming
http://www.softcircuits.com

[Chris Dunaway]

Tom Spink wrote:

While a string object is a reference object, it is classed as immutable,
meaning that you cannot modify it's value once it's created. The 'Trim'

I think the OP understood this. He was questioning the docs where it
said:

According to the intellisense help, string.Trim() "Removes all
occurances
or white space characters from the beginning and end
**** of this instance.***" (<----- NOTE this phrase here)

The docs seem to indicate that the Trim function should operate on the
instance of the string when in reality it does not, it returns a new
string. Perhaps Trim should have been a static method so that it was
not ambiguous"

s = String.Trim(s);

[Jonathan Wood]

Right. I'm not sure a static method would solve the issue. But I would
probably rewrite the help something like this:

"Returns a copy of this string with all occurances of white space characters
removed from the beginning and end."

--
Jonathan Wood
SoftCircuits Programming
http://www.softcircuits.com

"Chris Dunaway" <du******@gmail .comwrote in message
news:11******** **************@ h48g2000cwc.goo glegroups.com.. .

Tom Spink wrote:

>While a string object is a reference object, it is classed as immutable,
meaning that you cannot modify it's value once it's created. The 'Trim'

I think the OP understood this. He was questioning the docs where it
said:

According to the intellisense help, string.Trim() "Removes all
occurances
or white space characters from the beginning and end
**** of this instance.***" (<----- NOTE this phrase here)

The docs seem to indicate that the Trim function should operate on the
instance of the string when in reality it does not, it returns a new
string. Perhaps Trim should have been a static method so that it was
not ambiguous"

s = String.Trim(s);

[Jon Skeet [C# MVP]]

Jonathan Wood <jw***@softcirc uits.comwrote:

Right. I'm not sure a static method would solve the issue. But I would
probably rewrite the help something like this:

"Returns a copy of this string with all occurances of white space characters
removed from the beginning and end."

To be fair, the "Return value" section of both overloads is more
accurate:

"Return Value
A new String equivalent to this instance after white space characters
are removed from the beginning and end."

and

"Return Value
The String that remains after all occurrences of the characters in
trimChars are removed from the beginning and end of this instance. If
trimChars is a null reference (Nothing in Visual Basic), white space
characters are removed instead."

The summary is far from ideal though, I agree.

--
Jon Skeet - <sk***@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

[Tom Spink]

Chris Dunaway wrote:

Tom Spink wrote:

>While a string object is a reference object, it is classed as immutable,
meaning that you cannot modify it's value once it's created. The 'Trim'

I think the OP understood this. He was questioning the docs where it
said:

According to the intellisense help, string.Trim() "Removes all
occurances
or white space characters from the beginning and end
**** of this instance.***" (<----- NOTE this phrase here)

The docs seem to indicate that the Trim function should operate on the
instance of the string when in reality it does not, it returns a new
string. Perhaps Trim should have been a static method so that it was
not ambiguous"

s = String.Trim(s);

I guess it depends on your point of view... because yes, string.Trim() does
remove all occurrances of white space characters from the beginning and end
of the instance. That's exactly what it does. It just returns a new
instance with the changes, not /adjust/ the current instance.

--
Hope this helps,
Tom Spink

Google first, ask later.