Question

The following code

string expression = "(\\{[0-9]+\\})";
RegexOptions options = ((RegexOptions.IgnorePatternWhitespace | RegexOptions.Multiline) | RegexOptions.IgnoreCase);
Regex tokenParser = new Regex(expression, options);

MatchCollection matches = tokenParser.Matches("The {0} is a {1} and the {2} is also a {1}");

will match and capture “{0}”, “{1}”, “{2}” and “{1}”.

Is it possible to change it (either the regular expression or option of the RegEx) so that it would match and capture “{0}”, “{1}” and “{2}”. In other words, each match should only be captured once?

Answer 1

Here’s something you could use for a pure regex solution:

Regex r = new Regex(@"(\{[0-9]+\}|\[[^\[\]]+\])(?<!\1.*\1)",
                    RegexOptions.Singleline);

But for the sake of both efficiency and maintainability, you’re probably better off with a mixed solution like the one you posted.