Trying to using EF 6 with PostgreSQL - Failed to find or load the registered .Net Framework Data Provider

问题

I am trying to use EF 6 Code First with Npgsql provider. When I try to run Add-Migration command in package manager I have the following exception: Failed to find or load the registered .Net Framework Data Provider.

PM> Add-Migration -Force -ConfigurationTypeName "TestDbContextMigration" -ConnectionString "Server=localhost;Port=5432;Database=test_db;User Id=test;Password=konnaya;" -ConnectionProviderName "Npgsql" 
cmdlet Add-Migration at command pipeline position 1
Supply values for the following parameters:
Name: 123
System.Configuration.ConfigurationErrorsException: Failed to find or load the registered .Net Framework Data Provider.
   at System.Data.Common.DbProviderFactories.GetFactory(DataRow providerRow)
   at System.Data.Common.DbProviderFactories.GetFactory(String providerInvariantName)
   at System.Data.Entity.Infrastructure.DependencyResolution.DefaultProviderFactoryResolver.GetService(Type type, Object key, Func`3 handleFailedLookup)
   at System.Data.Entity.Infrastructure.DependencyResolution.DefaultProviderFactoryResolver.GetService(Type type, Object key)
   at System.Data.Entity.Infrastructure.DependencyResolution.CachingDependencyResolver.<>c__DisplayClass1.<GetService>b__0(Tuple`2 k)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at System.Data.Entity.Infrastructure.DependencyResolution.CachingDependencyResolver.GetService(Type type, Object key)
   at System.Data.Entity.Infrastructure.DependencyResolution.ResolverChain.<>c__DisplayClass3.<GetService>b__0(IDbDependencyResolver r)
   at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext()
   at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source, Func`2 predicate)
   at System.Data.Entity.Infrastructure.DependencyResolution.ResolverChain.GetService(Type type, Object key)
   at System.Data.Entity.Infrastructure.DependencyResolution.RootDependencyResolver.GetService(Type type, Object key)
   at System.Data.Entity.Infrastructure.DependencyResolution.ResolverChain.<>c__DisplayClass3.<GetService>b__0(IDbDependencyResolver r)
   at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext()
   at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source, Func`2 predicate)
   at System.Data.Entity.Infrastructure.DependencyResolution.ResolverChain.GetService(Type type, Object key)
   at System.Data.Entity.Infrastructure.DependencyResolution.CompositeResolver`2.GetService(Type type, Object key)
   at System.Data.Entity.Infrastructure.DependencyResolution.DbDependencyResolverExtensions.GetService[T](IDbDependencyResolver resolver, Object key)
   at System.Data.Entity.Internal.LazyInternalConnection.CreateConnectionFromProviderName(String providerInvariantName)
   at System.Data.Entity.Internal.LazyInternalConnection.InitializeFromConnectionStringSetting(ConnectionStringSettings appConfigConnection)
   at System.Data.Entity.Internal.LazyInternalConnection.Initialize()
   at System.Data.Entity.Internal.LazyInternalConnection.get_Connection()
   at System.Data.Entity.Internal.LazyInternalContext.get_Connection()
   at System.Data.Entity.Infrastructure.DbContextInfo..ctor(Type contextType, DbProviderInfo modelProviderInfo, AppConfig config, DbConnectionInfo connectionInfo, Func`1 resolver)
   at System.Data.Entity.Migrations.DbMigrator..ctor(DbMigrationsConfiguration configuration, DbContext usersContext, DatabaseExistenceState existenceState, Boolean calledByCreateDatabase)
   at System.Data.Entity.Migrations.DbMigrator..ctor(DbMigrationsConfiguration configuration)
   at System.Data.Entity.Migrations.Design.MigrationScaffolder..ctor(DbMigrationsConfiguration migrationsConfiguration)
   at System.Data.Entity.Migrations.Design.ToolingFacade.ScaffoldRunner.Run()
   at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
   at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
   at System.Data.Entity.Migrations.Design.ToolingFacade.Run(BaseRunner runner)
   at System.Data.Entity.Migrations.Design.ToolingFacade.Scaffold(String migrationName, String language, String rootNamespace, Boolean ignoreChanges)
   at System.Data.Entity.Migrations.AddMigrationCommand.Execute(String name, Boolean force, Boolean ignoreChanges)
   at System.Data.Entity.Migrations.AddMigrationCommand.<>c__DisplayClass2.<.ctor>b__0()
   at System.Data.Entity.Migrations.MigrationsDomainCommand.Execute(Action command)
Failed to find or load the registered .Net Framework Data Provider.

The Update-Database command gives the same result.

Sources https://github.com/DonTomato/PgEF

This is a simple example that does not contain anything superfluous for this topic.

回答1:

You need to have the Npgsql.dll, Mono.Security.dll and Npgsql.EntityFramework.dll assemblies added into the GAC as well as the following configuration added in the application's config file

<system.data>
  <DbProviderFactories>
    <remove invariant="Npgsql" />
    <add name="Npgsql Data Provider" invariant="Npgsql" support="FF" description=".Net Framework Data Provider for Postgresql" type="Npgsql.NpgsqlFactory, Npgsql" />
  </DbProviderFactories>
</system.data>
<entityFramework>
  <defaultConnectionFactory type="Npgsql.NpgsqlConnectionFactory, Npgsql" />
  <providers>
    <provider invariantName="Npgsql" type="Npgsql.NpgsqlServices, Npgsql.EntityFramework" />
  </providers>
</entityFramework>

来源：https://stackoverflow.com/questions/24340997/trying-to-using-ef-6-with-postgresql-failed-to-find-or-load-the-registered-ne