using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string xxx1 = "   \t   ";

        Console.WriteLine($"String xxx1: {xxx1.Length}   [{xxx1}]");

        string xxx2 = Regex.Replace(xxx1, @"[\s\t]", "");

        Console.WriteLine($"String xxx2: {xxx2.Length}   [{xxx2}]");

    }

}

​