using System;using System.Text; using System.Diagnostics; using System.Linq; 

​

public static class Program

{

    public static string RemoveWhiteSpace(this string s)

    {

        char[] r = new char[s.Length]; 

        int idxr = 0; 

        for (int i = 0; i < s.Length; i++) {

            if ( !Char.IsWhiteSpace(s[i])) {

                r[idxr] = s[i];

                idxr++;

            }

        }

        return new string(r); 

    }

    public static string StringBuilderRemoveWhiteSpace(this string s) {

        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < s.Length; i++) {

            if ( !Char.IsWhiteSpace(s[i])) {

                sb.Append(s[i]);

            }

        }

        return sb.ToString(); 

    }

    public static string LinqRemoveWhiteSpace(this string s) {

        return new string(s.ToCharArray().Where(c => !Char.IsWhiteSpace(c)).ToArray());

    }   

    //public static string NormalizeWhiteSpaceForLoop(this string input)

    public static string FastRemoveWhiteSpace(this string input)

    {

        int len = input.Length,

            index = 0,

            i = 0;

        var src = input.ToCharArray();

        //bool skip = false;

        char ch;

        for (; i < len; i++)

        {

            ch = src[i];

            switch (ch)

            {

                case '\u0020':

                case '\u00A0':

                case '\u1680':

                case '\u2000':

                case '\u2001':

                case '\u2002':

                case '\u2003':

                case '\u2004':

                case '\u2005':

                case '\u2006':

                case '\u2007':

                case '\u2008':

                case '\u2009':

                case '\u200A':

                case '\u202F':

                case '\u205F':

                case '\u3000':

                case '\u2028':

                case '\u2029':

                case '\u0009':

                case '\u000A':

                case '\u000B':

                case '\u000C':

                case '\u000D':

                case '\u0085':

                    //if (skip) continue;

                    //src[index++] = ch;

                    //skip = true;

                    continue;

                default:

                    //skip = false;

                    src[index++] = ch;

                continue;

            }

        }

​

        return new string(src, 0, index);

    }

    public static void Main()

    {

        Stopwatch sw = new Stopwatch(); 

        string test = "China lashes out at Hong Kong protest targeting its office Mon 22-Jul-19 10:33am"; 

        sw.Start();

        Console.WriteLine(test.RemoveWhiteSpace());

        sw.Stop(); 

        Console.WriteLine(sw.ElapsedTicks.ToString()+" ticks.");

        sw.Restart();

        Console.WriteLine(test.StringBuilderRemoveWhiteSpace());

        sw.Stop(); 

        Console.WriteLine(sw.ElapsedTicks.ToString()+" ticks.");

        sw.Restart();

        Console.WriteLine(test.LinqRemoveWhiteSpace());

        sw.Stop(); 

        Console.WriteLine(sw.ElapsedTicks.ToString()+" ticks.");

        sw.Restart();

        Console.WriteLine(test.FastRemoveWhiteSpace());

        sw.Stop(); 

        Console.WriteLine(sw.ElapsedTicks.ToString()+" ticks.");

    }

}