如何使用c#的REGEX删除字符之间的空格,制表符,换行符？

using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main()
    {
        string input = "Hello    World!\nThis is a\ttest.";
        string pattern = @"[\s\t\n]+";
        string replacement = "";

        string result = Regex.Replace(input, pattern, replacement);
        Console.WriteLine(result);
    }
}

HelloWorld!Thisisatest.