System.InvalidOperationException: 'Cannot resolve scoped service 'Microsoft.EntityFrameworkCore‘

 初學ASP.NET CORE,按照文檔練習，在使用SQL的時候代碼出現如下錯誤

System.InvalidOperationException
  HResult=0x80131509
  Message=Cannot resolve scoped service 'Microsoft.EntityFrameworkCore.DbContextOptions`1[WebApplication2.Models.WebApplication2Context]' from root provider.
  Source=Microsoft.Extensions.DependencyInjection
  StackTrace:
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteValidator.ValidateResolution(Type serviceType, IServiceScope scope, IServiceScope rootScope)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.Microsoft.Extensions.DependencyInjection.ServiceLookup.IServiceProviderEngineCallback.OnResolve(Type serviceType, IServiceScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService(Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
   at WebApplication2.Models.SeedData.Initialize(IServiceProvider serviceProvider) in C:\Users\guosiqi\source\repos\WebApplication2\WebApplication2\Models\SeedData.cs:line 18
   at WebApplication2.Startup.Configure(IApplicationBuilder app, IHostingEnvironment env) in C:\Users\guosiqi\source\repos\WebApplication2\WebApplication2\Startup.cs:line 71

這是因爲註冊的WebApplication2Context用的是Scope，但是在Scope外訪問WebApplication2Context，所以拋出了異常
在這個方法中單獨創建一個Scope

 public class SeedData
    {
        public static void Initialize(IServiceProvider serviceProvider)
        {
            //註冊的WebApplication2Context用的是Scope，但是在Scope外訪問WebApplication2Context，所以拋出了異常
            //在這個方法中單獨創建一個Scope
            using (var serviceScope = serviceProvider.CreateScope()) //手動高亮
            {
                using (var context = new WebApplication2Context(
                //這裏要使用serviceScope.ServiceProvider
                serviceScope.ServiceProvider.GetRequiredService<DbContextOptions<WebApplication2Context>>()))
                {
                    // Look for any movies.   
            }
        }
    }
}

問題解決