// @nuget: FluentAssertions

​

using System;

​

namespace Try_More_On_IEnumerable

{

    class Program

    {

        static void Main(string[] args)

        {

            T09获取一个链接字符串.Run();

            Console.WriteLine($"运行成功,{DateTime.Now:O}");

        }

    }

}

​

namespace Try_More_On_IEnumerable

{

    using System;

    using System.Collections.Generic;

    using System.Configuration;

    using System.IO;

    using System.Linq;

    using FluentAssertions;

​

    public class T09获取一个链接字符串

    {

        public static void Run()

        {

            // 获取一个当前可用的链接字符串

            var conn = GetConnectionString().FirstOrDefault();

            conn.Should().Be("Source=赛博坦;UID=月x;Password=******");

​

            IEnumerable<string> GetConnectionString()

            {

                // 从一个文件中获取链接字符串

                var connFilename = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "conn.txt");

                if (File.Exists(connFilename))

                {

                    var fileContent = File.ReadAllText(connFilename);

                    yield return fileContent;

                }

​

                // 从配置文件中读取链接字符串

                var dbConnectionString = ConfigurationManager.ConnectionStrings["db"]?.ConnectionString;

                if (!string.IsNullOrEmpty(dbConnectionString))

                {

                    yield return dbConnectionString;

                }

​

                // 返回默认的字符串

                yield return "Source=赛博坦;UID=月x;Password=******";

            }

        }

    }

}