using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string input = "Ramesh_123";

        if (System.Text.RegularExpressions.Regex.Match(input, @"[~`!@#$%^&*()-+=|\{}':;.,<>_/?]").Success)

            Console.WriteLine("Valid Input" +input);

        else

            Console.WriteLine("InValid Input -- Regex Fails : " +input);

        string output = Test(input);

    }

    private static readonly Regex Pattern = new Regex("{(.+?)}", RegexOptions.Compiled);

​

    public static string Test(string input)

    {

        return Pattern.Replace(input, match =>

        {

            string newMatch = match.Groups[1].Value;

            return ">> " + newMatch + " <<";

        });

    }

}