Recommendation on How to build a long string

[Mo]

Hi,

I am trying to write a code to build a string 768 characters long.
This string is going to be written to a file which is then read by
another application. The format of the string is already defined. For
example Firstname starts at position 20, Last Name at position 30,
address at position 40 etc... I am reading these data from sql
datasource and must substitute the values in the exact position
insuring that paramteres end up exactly at position they need to be. I
have this running now but I am looking for a smarter method. I am
trying to build a string with 768 spaces to initalize. Then replace
the spaces with characters one at a time to insure location of all
parameters are preserved. I tried using stringbuilder but it does not
have the functionality I am lookign for. Does Any body has a smart way
of dong this?

character Position
012345678901234 567890123456789 012345678901234 567890123456789 012345678901234 567890123456789
FirstName LastName Address
street City st Zip xxx xxxxx xxxx

Thanks,
Mo

[Bruce Wood]

On Mar 26, 6:39 pm, Göran Andersson <[e-mail] wrote:

Bruce Wood wrote:

On Mar 26, 2:18 pm, Göran Andersson <[e-mail] wrote:

Bruce Wood wrote:
On Mar 26, 2:20 am, Göran Andersson <[e-mail] wrote:
Mo wrote:
Hi,
I am trying to write a code to build a string 768 characters long.
This string is going to be written to a file which is then read by
another application. The format of the string is already defined. For
example Firstname starts at position 20, Last Name at position 30,
address at position 40 etc... I am reading these data from sql
datasource and must substitute the values in the exact position
insuring that paramteres end up exactly at position they need to be.. I
have this running now but I am looking for a smarter method. I am
trying to build a string with 768 spaces to initalize. Then replace
the spaces with characters one at a time to insure location of all
parameters are preserved. I tried using stringbuilder but it does not
have the functionality I am lookign for. Does Any body has a smart way
of dong this?
character Position
012345678901 234567890123456 789012345678901 234567890123456 789012345678901 234***567890123 456789
FirstName LastName Address
street City st Zip xxx xxxxx xxxx
Thanks,
Mo
Use the StringBuilder to build the string from left to right, instead of
trying to creating a string and put things into it.
Example:
StringBuild er record = new StringBuilder() ;
record.Append (firstName);
record.Append (' ', 40 - record.Length);
recoRd.Append (lastName);
record.Append (' ', 80 - recoed.Length);
...
string result = record.ToString ();
This looked promising until I noticed the following.
1. StringBuilder.A ppend doesn't have an Append signature for (string,
int).
Of course not, but it has an overload for Append(char, int), which is
what's used in the code.

Strings are delimited with quotes (").
Chars are delimited with apostrophes (').

Ouch. Need to reduce the resolution of my monitor, obviously. Didn't
notice the difference between ' and " in your code. Sorry.

>It does, however, have (string, int, int), where the first int
is the start location in the string, so, Göran's code is easily
changed:
StringBuilde r record = new StringBuilder() ;
record.Append( firstName);
record.Append( ' ', 0, 40 - record.Length);
record.Append( lastName);
record.Append( ' ', 0, 80 - record.Length);
...
string result = record.ToString ();
Nope. That doesn't even compile.

No, of course it wouldn't: I cut-and-pasted your code, assuming that
the char ' ' was in fact a string " ".

>However, this still doesn't work, because if firstName or lastName is
longer than the maximum length, then the resulting record will be
misaligned, and the second int argument, the number of characters to
append, will be negative. The latter will cause Append to throw an
ArgumentOutOfR ange exception.
So, you need to truncate the strings (if necessary), and _then_ do the
Append:
StringBuilde r record = new StringBuilder() ;
if (firstName.Leng th 40) firstName = firstName.Subst ring(0, 40);
record.Append( firstName);
record.Append( ' ', 0, 40 - record.Length);
if (lastName.Lengt h 80) lastName = lastName.Substr ing(0, 80);
record.Append( lastName);
record.Append( ' ', 0, 80 - record.Length);
...
string result = record.ToString ();
This is simpler, creates less strings and doesn't change the original
values:

StringBuilder record = new StringBuilder() ;
record.Append(f irstName, 0, Math.Min(firstN ame.Length, 40));
record.Append(' ', 40 - record.Length);
record.Append(l astName, 0, Math.Min(lastNa me.Length, 40));
record.Append(' ', 80 - record.Length);

It also has the added benefit of working. ;)

I know it's nit-picky, but your code and my code create the same
number of strings, I believe. The benefit of yours is that, as you
stated, it doesn't alter firstName or lastName.

Nope, my code creates a smaller (or sometimes equal) number of strings. :)

When you use Substring to truncate a string, it creates another string.
Instead I use the overload of the Append method that appends a part of a
string. This does not create an extra truncated string, but reads
directly from the original string.

Right you are.