using System;

using System.Text.RegularExpressions;               

public class Program

{

    public static void Main()

    {

        var input = @"hello Assdsfsd sdsfh23232 23322 2 323                             32323098

B

c           

c       

2@@@@@@###@#@

​

​

​

​

​

​

​

​

swrod";

        var firstOut = Regex.Replace(input, @"[^A-Za-z0-9@#]", " ");

        var m = Regex.Replace(firstOut,@"\s+"," ");

        Console.WriteLine(m);

    }

}