Question

Using c# I am trying to use regular expressions to get the value of a piece of text that appears after a colon. I know the field name, but there is a following colon that is in a variable position. The value would end at the next whitespace.

Thus:

KnownFieldName : Value

I’d then like to place the value into a group.

I’ve found a number of similar questions but none that actually points me in the direction of solving this.

This is part of a larger piece of code, but basically it fits in here:

     foreach (var v in fieldsToParse)
                {
                    var match = Regex.Match(line, v.pattern, RegexOptions.IgnorePatternWhitespace);

                    if (match.Success)
                        v.value = match.Groups[v.name].Value;
                }   

Answer 1

The regex you’re looking for should be something like (?<knownfieldname>[a-zA-Z]+)(\s+):(\s+)(?<value>[a-zA-Z]+) or knownfieldname(\s+):(\s+)(?<value>[a-zA-Z]+)

This presumes that KnownFieldName and Value are both only alpha characters, of course. If numerics can come into it you may also want to add 0-9 to the ranges, or if anything but white space is really valid there you can just use the \S wildcard I guess.

Edited to incorporate a variable number of spaces. Also, in light of the comments below, you might consider bookmarking both Derek Slager’s awesome Regex tester and this simple Regex cheat sheet. Helps a lot with situations like this.