using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string inputString = "Add any characters here that App FeedBack should filter and not allow...1/10 EP Sp'arrowha?wk XT R;TR 2.4GHz R\\ed!$()-+=, .";

        Regex re = new Regex("[^a-zA-Z0-9!$()-+=,. ]");

        string outputString = re.Replace(inputString, string.Empty);

        Console.WriteLine("Output: [{0}]",outputString);    

        inputString = string.Empty;

        re = new Regex("[^a-zA-Z0-9!$()-+=,. ]");

        outputString = re.Replace(inputString, string.Empty);

        Console.WriteLine("Output: [{0}]",outputString);        

    }

}