一些字符串的操作

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Test();
    }

    public void Test()
    {
        string str = "Now is the time for all good men to come to the aid of their party.";
        int start;
        int at;

        Console.WriteLine();
        Console.WriteLine("All occurrences of 't' from position 0 to {0}.", str.Length - 1);
        //Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str);
        Console.Write("The letter 't' occurs at position(s): ");

        at = 0;
        start = 0;
        //获取每个t的位置
        while ((start < str.Length) && (at > -1))
        {
            at = str.IndexOf('t', start);
            if (at == -1) break;
            Console.Write("{0} ", at);
            start = at + 1;
        }

        string a = "a bcde";
        int index = a.IndexOf('e');
        int index1 = a.IndexOf('e', 0);
        //获取带星号的ip
        string ip = "127.0.0.123";
        string ip2 = "123456";
        string index2 = ip2.Substring(0,3);
        string changeip = ip.Substring(0,ip.LastIndexOf(".")+1)+"*";

    }

}