正则表达式替换字符串

using System;
 
using System.Collections.Generic;
 
using System.Linq;
 
using System.Text;
 
using System.Text.RegularExpressions;
 
namespace ConsoleApplication3
 
{
 
    class Program
 
    {
 
        static void Main(string[] args)
 
        {
 
string s = "<ConnectString>Data Source=asdf, Database=fees</ConnectString>";
 
            Regex r = new Regex("(?<=<ConnectString>).*?(?=</ConnectString>)", RegexOptions.IgnoreCase);
 
            string result = r.Replace(s, "新字符串");
 
            Console.WriteLine(result);
 
            Console.ReadKey();
 
        }
 
    }
 
}

static void Main(string[] args) {
            string content = File.ReadAllText("D:\\1.txt", Encoding.Default);
            content = Regex.Replace(content, @"(?<=title>)(.*?)(?=</title>)", "你的字符");
            content = Regex.Replace(content, "(?<=style.*?>)[^<]*?(?=</style>)", "空为删除");
            Console.Write(content);
        }