Question

I have a regular expression in my code to match on the keys (control ClientId) within a form POST. I am looping round all the keys in the form data and performing the required action when a match is found.

However the regex is matching more times than I need it to. This runs on every request and if performing unnecessary code to fire.

Match match = Regex.Match(key.ToLower(), @"(?!\$)(?:[a-z0-9]+)$",
                          RegexOptions.Compiled);

Sample string that are coreectly matching

master$maincontentplaceholder$ucsearchresults$hdnvalue
master$maincontentplaceholder$ucsearchresults$hdnvalue2
master$maincontentplaceholder$ucsearchresults$hdnvalue3

I then have a switch statment with cases matching the control id

case: "hdnvalue"
case: "hdnvalue2"
case: "hdnvalue3"

The form is also returning a large number of extra keys that do not always require processing. It would be good if I could exclude these from being matched within the regex. (note the extra client id level $ucfilter)

master$maincontentplaceholder$ucsearchresults$ucfilter$hdnvalue
master$maincontentplaceholder$ucsearchresults$ucfilter$hdnvalue2
master$maincontentplaceholder$ucsearchresults$ucfilter$hdnvalue3

Answer 1

If you don’t /have/ to use regex, you might do better with LastIndexOf(“$”)

using System;

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            string text = "master$maincontentplaceholder$ucsearchresults$ucfilter$hdnvalue";
            string id = text.Substring(text.LastIndexOf("$") + 1);
            Console.WriteLine(id);
            Console.ReadLine();
        }
    }
}