给 iconfiguration 写一个 getappsetting 扩展方法

intro

在 .net core 中，微软已经默认使用 appsettings.json 来代替 app.config，并重新设计了一套完整的配置系统，可以支持 json/xml/ini/环境变量等。

在 .net core 中有一个 getconnectionstring 的扩展方法用来比较方便的获取链接字符串，类似于在 .net framework 中使用 configurationmanager.connectionstrings["key"] 来获取链接字符串。

这次来参考 getconnectionstring 实现一个 getappsetting，类似于 .net framework 中使用 configurationmanager.appsettings 来获取配置值。

实现代码

getconnectionstring 是获取 connectionstrings 这个节点下的某个配置，
getappsetting 来获取 appsettings 这个节点下的某个配置

实现代码：

        /// <summary>
        /// getappsetting
        /// shorthand for getsection("appsettings")[key]
        /// </summary>
        /// <param name="configuration">iconfiguration instance</param>
        /// <param name="key">appsettings key</param>
        /// <returns>app setting value</returns>
        public static string getappsetting([notnull]this iconfiguration configuration, string key)
        {
            return configuration.getsection("appsettings")[key];
        }

        /// <summary>
        /// getappsetting
        /// shorthand for getsection("appsettings")[key]
        /// </summary>
        /// <param name="configuration">iconfiguration instance</param>
        /// <param name="key">appsettings key</param>
        /// <returns>app setting value</returns>
        public static t getappsetting<t>([notnull]this iconfiguration configuration, string key)
        {
            return configuration.getsection("appsettings")[key].to<t>();
        }

        /// <summary>
        /// getappsetting
        /// shorthand for getsection("appsettings")[key]
        /// </summary>
        /// <param name="configuration">iconfiguration instance</param>
        /// <param name="key">appsettings key</param>
        /// <param name="defaultvalue">default value if not exist</param>
        /// <returns>app setting value</returns>
        public static t getappsetting<t>([notnull] this iconfiguration configuration, string key, t defaultvalue)
        {
            return configuration.getsection("appsettings")[key].toordefault(defaultvalue);
        }

        /// <summary>
        /// getappsetting
        /// shorthand for getsection("appsettings")[key]
        /// </summary>
        /// <param name="configuration">iconfiguration instance</param>
        /// <param name="key">appsettings key</param>
        /// <param name="defaultvaluefunc">default value func if not exist to get a default value</param>
        /// <returns>app setting value</returns>
        public static t getappsetting<t>([notnull] this iconfiguration configuration, string key, func<t> defaultvaluefunc)
        {
            return configuration.getsection("appsettings")[key].toordefault(defaultvaluefunc);
        }

查看源码

使用

使用起来和 getconnectionstring 差不多

测试 appsettings.json

{
  "connectionstrings": {
    "testdb": "server=.;database=test;uid=weihanli;pwd=admin888"
  },
  "appsettings":{
    "number": 12,
    "city": "shanghai"
  }
}

getappsetting 示例

        iconfiguration configuration = new configurationbuilder()
            // ...
            .addjsonfile("appsettings.json")
            .build();

        var city = configuration.getappsetting("city");
        var number = configuration.getappsetting<int>("number");
        system.console.writeline($"city:{city}, number:{number}");