下面我们给 IServiceCollection 写扩展方法

首先新建一个静态类 名称未 services,代码如下：

 1 public static class service
 2         {
 3         public  static IServiceCollection registerService(this IServiceCollection services)
 4         {
 5 
 6             services.AddSession();
 7            
 8             services.AddControllersWithViews();
 9             services.AddSingleton<hy_contentService>();
10             services.AddSingleton<UserService>();
11             services.AddSingleton<hy_roomService>();
12             services.AddSingleton<hy_classService>();
13             services.AddSingleton<hy_groupService>();
14             //sqlserver_personService
15             services.AddSingleton<sqlserver_personService>();
16             services.AddSingleton<Town_countryService>();
17             services.AddSingleton<sqlserver_departmentService>();
18             //TypeService
19             services.AddHttpContextAccessor();
20             services.AddRazorPages().AddRazorRuntimeCompilation();
21 
22 
23 
24 
25 
26             return services;
27         }
28     }

 在扩展类中新建一个   registerService方法 用于 扩展  ，方法签名如下：
            public  static IServiceCollection registerService(this IServiceCollection services)       

完整代码如下：

 1  public  static IServiceCollection registerService(this IServiceCollection services)
 2         {
 3         //将服务注册都可以写到该扩展方法中
 4             services.AddSession();
 5            
 6             services.AddControllersWithViews();
 7             services.AddSingleton<hy_contentService>();
 8             services.AddSingleton<UserService>();
 9             services.AddSingleton<hy_roomService>();
10             services.AddSingleton<hy_classService>();
11             services.AddSingleton<hy_groupService>();
12             //sqlserver_personService
13             services.AddSingleton<sqlserver_personService>();
14             services.AddSingleton<Town_countryService>();
15             services.AddSingleton<sqlserver_departmentService>();
16             //TypeService
17             services.AddHttpContextAccessor();
18             services.AddRazorPages().AddRazorRuntimeCompilation();
19 
20 
21 
22 
23 
24             return services;
25         }

下面 在 startUp ConfigureServices方法中使用  扩展方法

 1  public void ConfigureServices(IServiceCollection services)
 2         {
 3             DB.DB_ConnectionString = Configuration.GetConnectionString("mySqlStr");
 4             DB.DB_SqlserverConnectionString = Configuration.GetConnectionString("SqlServerStr"); //SqlServerStr
 5 
 6             services.registerService();  

 //该处调用 扩展方法 registerService ，把注册各种服务都可以写入该方法内 ，增强程序可读性 ，同时能保持  ConfigureServices 方法可读性。层次、逻辑更清晰
 7 
 8       }

扩展方法 定义及应用就写到这里！