Validate User input that is read in

Here's one way without using Regex: using System; namespace LimitDigits_CS { class Class1 { static void Main() { int code, x, n; string scode; bool dflag, cflag; char [] carry; do { dflag = false; cflag = false; Console.Write ("Enter a 6 digit number: "); scode = Console.ReadLine(); n = scode.Length; carry = new char [n]; carry = scode.ToCharArray(); if (n != 6) dflag = true; for (x = 0; x < n; x++) { if (!Char.IsDigit(carry[x])) cflag = true; } if (cflag == true) Console.WriteLine("Not a number"); else if (dflag == true) Console.WriteLine("Need 6 digits."); else { code = Convert.ToInt32(scode); Console.WriteLine("\nOK. Number is {0}", code); } Console.WriteLine(); } while (dflag == true || cflag == true); } } }