I am trying to get a Regex replacement working to update my AssemblyInfo.cs files, so I have:
Regex.Replace(
contents,
@"([assembly: Assembly(File)?Version("").*("")])",
"$1" + version + "$3"
);
The problem is that version is something like "1.5.3.0", so that when the replacement is evaluated it is seeing "$11.5.3.0$3" and is presumably looking for the eleventh captured group because it is coming out with:
$11.5.3.0")]
If is stick a space after the $1 it works fine. What do I need to put in there to escape the second digit without actually inserting the character?
Use ${1} instead of $1. This is also the substitution syntax for named capturing group (?<name>).
Here’s a snippet to illustrate (see also on ideone.com):
Console.WriteLine(Regex.Replace("abc", "(.)", "$11")); // $11$11$11
Console.WriteLine(Regex.Replace("abc", "(.)", "${1}1")); // a1b1c1
Console.WriteLine(Regex.Replace("abc", "(?<x>.)", "${x}1")); // a1b1c1
This behavior is explicitly documented:
Regular Expression Language Elements – Substitutions
Substituting a Numbered Group
The
$numberlanguage element includes the last substring matched by thenumbercapturing group in the replacement string, wherenumberis the index of the capturing group.If
numberdoes not specify a valid capturing group defined in the regular expression pattern,$numberis interpreted as a literal character sequence that is used to replace each match.Substituting a Named Group
The
${name}language element substitutes the last substring matched by thenamecapturing group, wherenameis the name of a capturing group defined by the(?<name>)language element.If
namedoes not specify a valid named capturing group defined in the regular expression pattern,${name}is interpreted as a literal character sequence that is used to replace each match.
4