IConfigurationBuilder用於Build IConfigurationRoot(從IConfiguration繼承) 物件。IConfigurationBuilder介面中維護了一系列的IConfigurationSource列表， 每種IConfigurationSource提供配置項的資料來源，IConfigurationSource.Build生成的IConfigurationProvider用於從當前配置源中讀取key-value值

static void Main(string[] args)
        {
            //1、建立IConfigurationBuilder
            IConfigurationBuilder builder = new ConfigurationBuilder();

            //2、建立配置源並新增到Builder中 IConfigurationSource

            //2、1系統自帶的IConfigurationSource
            List<KeyValuePair<string, string>> InitialData = new List<KeyValuePair<string, string>>();
            InitialData.Add(new KeyValuePair<string, string>("name", "caoruipeng"));
            InitialData.Add(new KeyValuePair<string, string>("info:age", "29"));
            InitialData.Add(new KeyValuePair<string, string>("info:school", "北華大學"));
            InitialData.Add(new KeyValuePair<string, string>("user:name", "北華大學"));
            IConfigurationSource source = new MemoryConfigurationSource() { InitialData = InitialData };
            builder.Add(source);

            //2、2自定義IConfigurationSource
            IDictionary<string, string> data = new Dictionary<string, string>();
            data.Add("dbkey", "dbvalue");
            IConfigurationSource dbSource = new DBConfigurationSource(data);
            builder.Add(dbSource);

            //3、建立key-value集合
            IConfigurationRoot configuration = builder.Build();

            //4、獲取key-value
            string value = configuration["name"];
            value = configuration.GetValue<string>("name");
            Console.WriteLine($"key:name,value:{value}");
            value = configuration.GetValue<string>("dbkey");
            Console.WriteLine($"key:dbkey,value:{value}");

            IConfigurationSection section = configuration.GetSection("info");
        }
    /// <summary>
    /// 自定義配置源
    /// </summary>
    public class DBConfigurationSource : IConfigurationSource
    {
        IDictionary<string, string> data = new Dictionary<string, string>();
        public DBConfigurationSource(IDictionary<string, string> data)
        {
            this.data = data;
        }
        public IConfigurationProvider Build(IConfigurationBuilder builder)
        {
            return new DBConfigurationProvider(data);
        }
    }
    /// <summary>
    /// 自定義配置源的Provider，用於從配置源中讀取key-value值
    /// </summary>
    public class DBConfigurationProvider : ConfigurationProvider
    {
        public DBConfigurationProvider(IDictionary<string, string> data)
        {
            Data = data;
        }
        public override void Load()
        {
            base.Load();
        }
    }