实体框架+ PostgreSQL代码优先

Question

这里第一次。我想实体框架与PostgreSQL的使用Visual Studio 2017年社区整合：

从的NuGet，我安装了这个软件包：

• EntityFramework.6.1.3
• Npgsql.3.2.2
• EntityFramework6.Npgsql.3.1.1

我的项目是一个Web API使用的.NET Framework 4.6.2（非核心）

我web.config看起来像这样

<system.data> 
    <DbProviderFactories> 
     <remove invariant="Npgsql"/> 
     <add name="Npgsql Data Provider" invariant="Npgsql" support="FF" description="Data Provider for PostgreSQL" type="Npgsql.NpgsqlFactory, Npgsql, Version=4.0.2.0, Culture=neutral, PublicKeyToken=5D8B90D52F46FDA7"/> 
    </DbProviderFactories> 
</system.data> 
<entityFramework> 
    <defaultConnectionFactory type="Npgsql.NpgsqlConnectionFactory, Npgsql"/> 
    <providers> 
     <provider invariantName="Npgsql" type="Npgsql.NpgsqlServices, EntityFramework6.Npgsql"/> 
    </providers> 
</entityFramework> 

但是，在包的NuGet管理器的控制台，发行后Enable Migrations，我得到这个错误：

Checking if the context targets an existing database...
System.Configuration.ConfigurationErrorsException: Failed to find or load the registered .Net Framework Data Provider.

in System.Data.Common.DbProviderFactories.GetFactory(DataRow providerRow)
in System.Data.Common.DbProviderFactories.GetFactory(String providerInvariantName)
in System.Data.Entity.Infrastructure.DependencyResolution.DefaultProviderFactoryResolver.GetService(Type type, Object key, Func 3 handleFailedLookup)
in System.Data.Entity.Infrastructure.DependencyResolution.DefaultProviderFactoryResolver.GetService(Type type, Object key)
in System.Data.Entity.Infrastructure.DependencyResolution.CachingDependencyResolver.<>c__DisplayClass1.<GetService>b__0(Tuple 2 k)
in System.Collections.Concurrent.ConcurrentDictionary 2.GetOrAdd(TKey key, Func 2 valueFactory)
in System.Data.Entity.Infrastructure.DependencyResolution.CachingDependencyResolver.GetService(Type type, Object key)
in System.Data.Entity.Infrastructure.DependencyResolution.ResolverChain.<>c__DisplayClass3.b__0(IDbDependencyResolver r)
in System.Linq.Enumerable.WhereSelectArrayIterator 2.MoveNext()
in System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable 1 source, Func 2 predicate)
in System.Data.Entity.Infrastructure.DependencyResolution.ResolverChain.GetService(Type type, Object key)
in System.Data.Entity.Infrastructure.DependencyResolution.RootDependencyResolver.GetService(Type type, Object key)
in System.Data.Entity.Infrastructure.DependencyResolution.ResolverChain.<>c__DisplayClass3.<GetService>b__0(IDbDependencyResolver r)
in System.Linq.Enumerable.WhereSelectArrayIterator 2.MoveNext()
in System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable 1 source, Func 2 predicate)
in System.Data.Entity.Infrastructure.DependencyResolution.ResolverChain.GetService(Type type, Object key)
in System.Data.Entity.Infrastructure.DependencyResolution.CompositeResolver 2.GetService(Type type, Object key)
in System.Data.Entity.Infrastructure.DependencyResolution.DbDependencyResolverExtensions.GetService[T](IDbDependencyResolver resolver, Object key)
in System.Data.Entity.Internal.LazyInternalConnection.CreateConnectionFromProviderName(String providerInvariantName)
in System.Data.Entity.Internal.LazyInternalConnection.InitializeFromConnectionStringSetting(ConnectionStringSettings appConfigConnection)
in System.Data.Entity.Internal.LazyInternalConnection.TryInitializeFromAppConfig(String name, AppConfig config)
in System.Data.Entity.Internal.LazyInternalConnection.Initialize()
in System.Data.Entity.Internal.LazyInternalConnection.get_Connection()
in System.Data.Entity.Internal.LazyInternalContext.get_Connection()
in System.Data.Entity.Infrastructure.DbContextInfo..ctor(Type contextType, DbProviderInfo modelProviderInfo, AppConfig config, DbConnectionInfo connectionInfo, Func 1 resolver)
in System.Data.Entity.Migrations.DbMigrator..ctor(DbMigrationsConfiguration configuration, DbContext usersContext, DatabaseExistenceState existenceState, Boolean calledByCreateDatabase)
in System.Data.Entity.Migrations.DbMigrator..ctor(DbMigrationsConfiguration configuration)
in System.Data.Entity.Migrations.Design.MigrationScaffolder..ctor(DbMigrationsConfiguration migrationsConfiguration)
in System.Data.Entity.Migrations.Design.ToolingFacade.ScaffoldRunner.Run()
in System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
in System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
in System.Data.Entity.Migrations.Design.ToolingFacade.Run(BaseRunner runner)
in System.Data.Entity.Migrations.Design.ToolingFacade.ScaffoldInitialCreate(String language, String rootNamespace)
in System.Data.Entity.Migrations.EnableMigrationsCommand.<>c__DisplayClass2.<.ctor>b__0()
in System.Data.Entity.Migrations.MigrationsDomainCommand.Execute(Action command)

Failed to find or load the registered .Net Framework Data Provider.

你能帮助我吗？

在此先感谢。

Answer 1

尝试使用Windows安装程序将Npgsql安装到GAC。这可以帮助很多时间。

Download

此外，使用检查在DbProviderFactories版本号：

typeof(Npgsql.NpgsqlFactory).AssemblyQualifiedName 

，并确保它们匹配。

Answer 2

我用了这个教程前段时间 http://rob.conery.io/2014/02/05/using-entity-framework-6-with-postgresql/