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}");