C# Regex.Replace (or String.Replace) only partially works

Question

I run a repeated Regex.Replace over a string, replacing certain "variables" with their "values". Thing is, some get replaced and some don't!
I have to analyze certain batch files (IBM JCL batch language, to be precise) and search them for JCL variables (rules: JCLvariable starts with "&" and ends with space; ","; "." or other variable start, that being "&"). My functions is supposed to take the string with variables and array of variables-and-their-values as an input; then search the string and replace JCL variables with their values. So is I run a forcycle and for each value-variable struct in array, I run Regex.Replace (in order to prevent the "&TOSP." being misplaced for "&TO." and adhere to JCL var rules, see above):

private string ReplaceDSNVarsWithValues(string _DSN,JCLvar[] VarsAndValues)
{
//FIXME: nefunguje pro TIPfile a nebere všechny &var
for(int Fa=0;Fa<VarsAndValues.Length/2;++Fa)
{               
    _DSN = Regex.Replace(_DSN, "&"+VarsAndValues[Fa].JCLvariable+"[^A-Za-z0-9]", VarsAndValues[Fa].JCLvalue);
}
return _DSN;
}

Eg. I have this as a string to replace:

string _DSN = "&TOSP..COPY.&SYSTEM..SP&APL..BVSIN.SAVEC.D&MES.&DEN..V&VER.K99";

And then I have an array of struct containing couples of variable and value, eg.

JCLvar[1].variable = "APL",JCLvar[1].value = "PROD"

Combine that and it should result in the "SP&APL." part changing to "SPPROD".

The problem is, only SOME of the variables get replaced: &TOSP..COPY.&SYSTEM..SP&APL..BVSIN.SAVEC.D&MES.&DEN..V&VER.K99 gets changed to SP.COPY.DBA0.SPPROD.BVSIN.SAVEC.D&MESDENV&VER.K99 as it should (disregard &MES,&DEN - these are not filled in the ValsAnd Values array and therefore don't get replaced), but in
&TO.[email protected]&MES.U&DEN..SUC.RES, the "&TO." doesn't get changed at all - although it exists in the array and via debugging, I see that it is being passed to the regex /but it doesn't get changed/.

How the heck it comes SOME variables get replaced and others don't? In the array VarsAndValues, order of variables matters, because if "TOSP" is first, it gets replaced and "&TO" does not, while if "TO" is first, it gets replaced and "&TOSP" doesn't; therefore, I got suspicion that Regex.Replace somehow fails to do repeated replace on similar expressions/variables in the same string OR fails to recognize the variable/expression to be replaced - but I see no reason for the first possibility and the second one is impossible, as the replaced expressions clearly stay there. //Note - I know it's certainly not nice coding, but it's more a single-purpose script I wrote to save me weeks of manual work than anything else

Tim Pietzcker · Accepted Answer · 2011-02-01 10:45:35Z

2

I don't see anything wrong with your regex. But why are you iterating over only half of VarsAndValues?

for(int Fa=0;Fa<VarsAndValues.Length/2;++Fa)

tells me you're stopping halfway through the array, so if TOSP happens to fall in the second half, it won't be replaced.

answered Feb 1, 2011 at 10:45

Tim Pietzcker

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TFG Over a year ago

Thanks a lot, it works now. (I actually reverted to the JCLvar struct from 2D array [thus Lenght/2] and thinking of other symptoms, I was too blind to realize this leftover. Guess I just needed an independent code review - I was stuck with this issue for over a day)

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