C#字符串截取

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication4
{
    class Program
    {

        static void Main(string[] args)
        {
            string a = "aaa.bbb.ccc";
            string b = a.Substring(1,5);
            Console.WriteLine(b);
        }
    }
}