在 ASP.NET Core 2.0 预览版中使用 Pomelo MySQL EF 提供程序时出错

Question

我在 ASP.NET Core 2.0 Preview 上使用 Pomelo 1.1.2，同时使用 EF 2.0 Preview。使用他们的演示代码，每次调用 "UseMySql":

时都会出现以下异常

System.TypeLoadException occurred
  HResult=0x80131522
  Message=Method 'Clone' in type 'Microsoft.EntityFrameworkCore.Internal.MySqlOptionsExtension' from assembly 'Pomelo.EntityFrameworkCore.MySql, Version=1.1.1.0, Culture=neutral, PublicKeyToken=null' does not have an implementation.
  Source=<Cannot evaluate the exception source>
  StackTrace:
   at Microsoft.EntityFrameworkCore.MySqlDbContextOptionsExtensions.UseMySql(DbContextOptionsBuilder optionsBuilder, String connectionString, Action`1 mySqlOptionsAction)
   at CoreTest1.Startup.<ConfigureServices>b__4_0(DbContextOptionsBuilder options) in C:\DEV\Experiments\CoreTest1\CoreTest1\Startup.cs:line 27
   at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.<>c__DisplayClass0_0`1.<AddDbContext>b__0(IServiceProvider p, DbContextOptionsBuilder b)
   at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.DbContextOptionsFactory[TContext](IServiceProvider applicationServiceProvider, Action`2 optionsAction)
   at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.<>c__DisplayClass5_0`1.<AddCoreServices>b__0(IServiceProvider p)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitFactoryService(FactoryService factoryService, ServiceProvider provider)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(IServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProvider provider)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitSingleton(SingletonCallSite singletonCallSite, ServiceProvider provider)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(IServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProvider provider)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(IServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProvider provider)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(IServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.<>c__DisplayClass17_0.<RealizeService>b__0(ServiceProvider provider)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetService[T](IServiceProvider provider)
   at CoreTest1.Controllers.HomeController.Index() in C:\DEV\Experiments\CoreTest1\CoreTest1\Controllers\HomeController.cs:line 18
   at Microsoft.AspNetCore.Mvc.Internal.ObjectMethodExecutor.Execute(Object target, Object[] parameters)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeActionMethodAsync>d__18.MoveNext()

想知道这是否只是因为 2.0 预览库？有任何想法吗？我试图在 Git 上查看他们的源代码，看看我是否能立即发现任何错误，但我做不到。

Answer 1

让我们看看 EF Core 2.0 预览版 1 announcement:

If you are using a third party database provider, then check to see if they have released an update that depends on 2.0.0-preview1-final. If they have, then just upgrade to the new version. If not, then you will not be able to upgrade since version 2.0 contains several breaking changes and 1.* providers are not expected to work with it.

这意味着 Pomelo 预计不会支持 EF Core 2.0，直到出现可比较的 release 被生产。

Answer 2

最近，我的项目更新到 .NET Core 2.0 时遇到了同样的错误。此时，https://github.com/PomeloFoundation/Pomelo.EntityFrameworkCore.MySql中描述了解决方案基本上，更新包到预发布版本 2.0.0-rc-*

<PackageReference Include="Pomelo.EntityFrameworkCore.MySql" Version="2.0.0-rc-*" />

Answer 3

如果您使用的是asp.net core 2.0，则需要使用pomelo 2.0.0。 Asp.net core 2.0 不适用于 pomelo 2.1 或更高版本。

在 ASP.NET Core 2.0 预览版中使用 Pomelo MySQL EF 提供程序时出错

Errors using Pomelo MySQL EF provider with ASP.NET Core 2.0 Preview

mysql

entity-framework-core

asp.net-core

asp.net-core-2.0

pomelo-entityframeworkcore-mysql