using System;    

using System.Text.RegularExpressions;    

namespace RegularExpression1    

{    

    public class Program    

    {    

        public static void Main(string[] args)    

        {       

            Regex r = new Regex(@"^\+?\d{0,2}\-?\d{4,5}\-?\d{5,6}");    

            string[] str = { "+91-9678967101", "9678967101", "+91-9678-967101", "+91-96789-67101", "+919678967101"};    

            foreach(string s in str)    

            {    

                Console.WriteLine("{0} {1} a valid mobile number.", s, r.IsMatch(s) ? "is":"is not");    

            }    

        }    

    }    

}