using System;

using System.Collections.Generic;

using System.IO;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Text.RegularExpressions;               

​

public class Program

{

    public static void Main()

    {

        string text = "80202";

        string pattern = @"^\d{5}$";

        var status = Regex.Match(text, pattern).Success;

        Console.WriteLine(String.Format("Is Zip Code ({0}) -> {1}", text, status));

    }

}