尝试在与 Pomelo.EntityFrameworkCore.MySql 相关的 dotnet core 3.1 中添加迁移时出错

Question

我收到此错误时，

dotnet ef migrations add InitialMigration

---

来自程序集“Pomelo.EntityFrameworkCore.MySql，版本=3.2.3.0，Culture=neutral，PublicKeyToken=2cc498582444921b”的“Pomelo.EntityFrameworkCore.MySql.Query.ExpressionVisitors.Internal.MySqlSqlTranslatingExpressionVisitorFactory”类型中的方法“Create”没有实现。

Entity Framework Core .NET 命令行工具 5.0.0-rc.2.20475.6

完全错误 -

Build started...
Build succeeded.
System.TypeLoadException: Method 'Create' in type 'Pomelo.EntityFrameworkCore.MySql.Query.ExpressionVisitors.Internal.MySqlSqlTranslatingExpressionVisitorFactory' from assembly 'Pomelo.EntityFrameworkCore.MySql, Version=3.2.3.0, Culture=neutral, PublicKeyToken=2cc498582444921b' does not have an implementation.
   at Microsoft.Extensions.DependencyInjection.MySqlServiceCollectionExtensions.AddEntityFrameworkMySql(IServiceCollection serviceCollection)    
   at Pomelo.EntityFrameworkCore.MySql.Infrastructure.Internal.MySqlOptionsExtension.ApplyServices(IServiceCollection services)
   at Microsoft.EntityFrameworkCore.Internal.ServiceProviderCache.ApplyServices(IDbContextOptions options, ServiceCollection services)
   at Microsoft.EntityFrameworkCore.Internal.ServiceProviderCache.<>c__DisplayClass4_0.<GetOrAdd>g__BuildServiceProvider|3()
   at Microsoft.EntityFrameworkCore.Internal.ServiceProviderCache.<>c__DisplayClass4_0.<GetOrAdd>b__2(Int64 k)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at Microsoft.EntityFrameworkCore.Internal.ServiceProviderCache.GetOrAdd(IDbContextOptions options, Boolean providerRequired)
   at Microsoft.EntityFrameworkCore.DbContext..ctor(DbContextOptions options)
   at Commander.Data.CommanderContext..ctor(DbContextOptions`1 opt) in D:\.NET\project02\data\CommanderContext.cs:line 8
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext 
context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitCache(ServiceCallSite callSite, RuntimeResolverContext context, ServiceProviderEngineScope serviceProviderEngine, RuntimeResolverLock lockType)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScopeCache(ServiceCallSite singletonCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine.<>c__DisplayClass1_0.<RealizeService>b__0(ServiceProviderEngineScope scope) 
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetServiceOrCreateInstance(IServiceProvider provider, Type type)
   at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.<>c__DisplayClass13_3.<FindContextTypes>b__11()
   at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(Func`1 factory)
   at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(String contextType)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType, String namespace)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType, String namespace)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigration.<>c__DisplayClass0_0.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
   at 

Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
Method 'Create' in type 'Pomelo.EntityFrameworkCore.MySql.Query.ExpressionVisitors.Internal.MySqlSqlTranslatingExpressionVisitorFactory' from assembly 'Pomelo.EntityFrameworkCore.MySql, Version=3.2.3.0, Culture=neutral, PublicKeyToken=2cc498582444921b' does not have an implementation.

---

依赖关系 -

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="5.0.0-rc.2.20475.6" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="5.0.0-rc.2.20475.6">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
      <PrivateAssets>all</PrivateAssets>
    </PackageReference>
    <PackageReference Include="Pomelo.EntityFrameworkCore.MySql" Version="3.2.3" />
    <PackageReference Include="Pomelo.EntityFrameworkCore.MySql.Design" Version="1.1.2" />
  </ItemGroup>


</Project>

appsetting.js

 "ConnectionStrings": 
  {
    "DefaultConnection": "server=localhost;port=3306;database=CommanderDB;uid=root;password=ishanah"
  }

启动.cs -

  public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();

            services.AddDbContext<CommanderContext>(options =>
        options.UseMySql(Configuration.GetConnectionString("DefaultConnection")));

            services.AddScoped<ICommanderRepo, MockCommanderRepo> ();
        }

Answer 1

Pomelo3.2.3与 EF Core 5 不兼容（请参阅兼容性）。您目前需要使用Alpha抢鲜从nuget.org我们从我们的每日构建饲料使用EF Core 5的。

有关更多信息，请查看EF Core 5 Preview 支持：

Answer 2

我已经解决了这个问题。只需为 EF core 和 Pomelo.EntityFrameworkCore.MySql 升级相同版本：5.x。请注意，您应该在 5.0 alpha 1 版本（而不是 alpha 2）中使用 Pomelo 才能使启动文件正确运行。