//在应用程序的任何地方注入 IConfiguration 来访问配置数据。ASP.NET Core 默认会加载 appsettings.json 文件

IConfiguration _configuration = builder.Configuration;
string connectionString =  _configuration["ConnectionStrings:SqlServerConnection"];

Helper帮助类

        private static IConfigurationRoot Configuration { get; set; }

        static ConfigurationTools()
        {
            var builder = new ConfigurationBuilder()
                .SetBasePath(Directory.GetCurrentDirectory())
                .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true);

            Configuration = builder.Build();
        }

        /// <summary>
        /// 默认获取ConnectionStrings节点下配置
        /// </summary>
        /// <param name="name"></param>
        /// <returns></returns>
        public static string GetConnectionString(string name)
        {
            return Configuration.GetConnectionString(name);
        }


        /// <summary>
        /// 将Key查询的数据自动封装成类
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="key"></param>
        /// <returns></returns>
        public static T GetAppSetting<T>(string key)
        {
            return Configuration.GetSection(key).Get<T>();
        }