using System;

using System.Text.RegularExpressions;

​

​

public class Program

{

    public static void Main(string[] args)

    {

        string str = "welcome@to-qa-with-experts#.com";

        string replacestr= Regex.Replace(str, "[^a-zA-Z0-9_]+", " ");

        Console.WriteLine(replacestr);

        Console.ReadLine();

    }

}

​