Regular expression to skip character in capture group

In short: You can't. A match is always consecutive, even when it contains things as zero-width assertions there is no way around matching the next character if you want to get to the one after it.

There really isn't a way to create an expression such that the matched text is different than what is found in the source text. You will need to remove the hyphen in a separate step either by matching the first and second parts individually and concatenating the two groups:

match = Regex.Match( text, "([A-B]{2,3})-([0-9]{2,3})" );
matchedText = string.Format( "{0}{1}", 
    match.Groups.Item(1).Value, 
    match.Groups.Item(2).Value );

Or by removing the hyphen in a step separate from the matching process:

match = Regex.Match( text, "[A-B]{2,3}-[0-9]{2,3}" );
matchedText = match.Value.Replace( "-", "" );

Your assertion that its not possible to do without sub-grouping + concatentating it is correct.

You could also do as Jeff-Hillman and merely strip out the bad character(s) after the fact.

Important to note here tho, is you "dont use regex for everything".

Regex is designed for less complicated solutions for non-trivial problems, and you shouldn't use "oh, we'll use a regex" for everything, and you shoudn't get into the habbit of thinking you can solve the problem in a one-step regex.

When there is a viable trivial method that works, by all means, use it.

An alternative Idea, if you happen to be needing to return multiple matches in a body of code is look for your languages "callback" based regex, which permits passing any matched/found group to a function call which can do in-line substitution. ( Especially handy in doing regexp replaces ).

Not sure how it would work in .Net, but in php you would do something like ( not exact code )

  function strip_reverse( $a )
  {
     $a = preg_replace("/-/", "", $a );
     return reverse($a);
  }
  $b = preg_replace_callback( "/(AB[-]?cde)/" , 'strip_reverse' , "Hello World AB-cde" ; 

Kind of late, but I think I figured this one out. At least one way to do it.

I used positive lookahead to stop at the # sign in my text. I didn't want the space or the # sign, so I had to figure a way out to "skip" over them. So when I was forced to match them again, I dumped them into a garbage group that I didn't plan on using (.ie, a bit bucket) which in the code is . Now, my place pointer is one character position beyond the # sign (where I want to be, skipping the space and the # sign). And I now just match to the end of the file name at the . and ignore the file extension.

(?i)English\\(?<Series>[^ ]+) - (?<Title>.+(?= #))(?<garb1>..)(?<Number>[^.]+)(?-i)

The Filename this was used on is

F:\Downloads\Downloads\500 Comics CCC CBR English\Isukani - Great Girl #01.cbr

I am kind of new to this, but you could use the vertical bar symbol |, which acts as an OR.

This could work for .NET:

((?<=[A-Z]{2}-)\d\d\d)|([A-Z]{2}(?=-\d\d\d))

This works for me in a VIM syntax file:

\(\([A-Z]\{2}-\)\@<=\d\d\d\)\|\([A-Z]\{2}\(-\d\d\d\)\@=\)