依赖注入之IConfiguration

  public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
            //下面这行就是注入
            services.Configure<AppSettings>(Configuration.GetSection("AppSettings"));//这里是添加的，其余的都是新建项目带的
         //AppSettings这个类是新增的，里面的字段，对应appsettings.json中的字段

          //链接字符串的
            var conn = Configuration.GetSection("ConnectionStrings");
            string efconn = conn["acc_miniehub"];  
             //映射的实体类的ConnectionString   属性
            OMSECData.Acc_OmsContext.ConnectionString = efconn;
            services.AddDbContext<OMSECData.Acc_OmsContext>
            (
                options => options.UseSqlServer(efconn)
            );


        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseMvc();
        }
    }

var builder = new ConfigurationBuilder()
               .SetBasePath(env.ContentRootPath)
               .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
               .AddEnvironmentVariables();
Configuration = builder.Build();
services.AddSingleton<IConfiguration>(Configuration);