Fixed regex, C# - rextester

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            List<string> filters = new List<string>();
            List<string> matches = new List<string>();
            
            string sentence = "This is a 01 02 03 (01) (02) (03) no01 no02 no03 test";
            string newSentence = string.Empty;

// Create Filters List
            for (int i = 0; i < 101; i++)
            {
                filters.Add(string.Format("{0:00}", i)); // 01-100
            }
            
            // Find Matches
            for (int i = 0; i < filters.Count; i++)
            {
                // Add to Matches List
                if (sentence.Contains(filters[i]))
                {
                    matches.Add(filters[i]);
                }
            }
            
            // Filter Sentence
            newSentence = Regex.Replace(
                sentence
            ,   @"(?<=\s|^)(" + string.Join("|", matches) + @")(?=\s|$)"
            ,   ""
            ,   RegexOptions.IgnoreCase
            );
            
            // Display Old Sentence
            //Console.WriteLine(sentence);
            
            // Display New Sentence
            Console.WriteLine(newSentence);
            
            // Display Matches
            //Console.WriteLine(string.Join("\n", matches));
            
            // Display Filters
            //Console.WriteLine(string.Join("\n", filters));
        }
    }
}

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Compilation time: 0,14 sec, absolute running time: 0,16 sec, cpu time: 0,16 sec, average memory usage: 18 Mb, average nr of threads: 4