使用實體框架訪問 MySQL 數據庫時出現異常

Question

我正在嘗試使用我的 .NET Framework Web 應用程序來處理實體框架和 MySQL 數據庫

我按照本文中使用 MySql 啟用實體框架的步驟進行了操作： https : //dev.mysql.com/doc/connector-net/en/connector-net-entityframework60.html

在我嘗試之前，這一切看起來都是彩虹獨角獸和陽光：

1. 在包管理器控制台中enable-migrations Add-Migration后執行Add-Migration 。
2. 啟動網絡應用程序。

我使用以下組件：

• .NET Framework 4.5.2
• Entity Framework 6.2.0
• MySql.Data.Entity 6.10.8
• MySQL database 5.7

我收到以下錯誤：

添加遷移錯誤：

System.NullReferenceException: Object reference not set to an instance of an object.
   at MySql.Data.MySqlClient.MySqlProviderServices.GetDbProviderManifestToken(DbConnection connection)
   at System.Data.Entity.Core.Common.DbProviderServices.GetProviderManifestToken(DbConnection connection)
   at MySql.Data.Entity.MySqlManifestTokenResolver.ResolveManifestToken(DbConnection connection)
   at System.Data.Entity.Utilities.DbConnectionExtensions.GetProviderInfo(DbConnection connection, DbProviderManifest& providerManifest)
   at System.Data.Entity.DbModelBuilder.Build(DbConnection providerConnection)
   at System.Data.Entity.Internal.LazyInternalContext.CreateModel(LazyInternalContext internalContext)
   at System.Data.Entity.Internal.RetryLazy`2.GetValue(TInput input)
   at System.Data.Entity.Internal.LazyInternalContext.InitializeContext()
   at System.Data.Entity.Internal.LazyInternalContext.get_ModelBeingInitialized()
   at System.Data.Entity.Infrastructure.EdmxWriter.WriteEdmx(DbContext context, XmlWriter writer)
   at System.Data.Entity.Utilities.DbContextExtensions.<>c__DisplayClass1.<GetModel>b__0(XmlWriter w)
   at System.Data.Entity.Utilities.DbContextExtensions.GetModel(Action`1 writeXml)
   at System.Data.Entity.Utilities.DbContextExtensions.GetModel(DbContext context)
   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.RunCore()
   at System.Data.Entity.Migrations.Design.ToolingFacade.BaseRunner.Run()
Object reference not set to an instance of an object.

Web 應用程序數據訪問錯誤：

Object reference not set to an instance of an object.
   at MySql.Data.MySqlClient.MySqlProviderServices.GetDbProviderManifestToken(DbConnection connection)
   at System.Data.Entity.Core.Common.DbProviderServices.GetProviderManifestToken(DbConnection connection)
   at MySql.Data.Entity.MySqlManifestTokenResolver.ResolveManifestToken(DbConnection connection)
   at System.Data.Entity.Utilities.DbConnectionExtensions.GetProviderInfo(DbConnection connection, DbProviderManifest& providerManifest)
   at System.Data.Entity.DbModelBuilder.Build(DbConnection providerConnection)
   at System.Data.Entity.Internal.LazyInternalContext.CreateModel(LazyInternalContext internalContext)
   at System.Data.Entity.Internal.RetryLazy`2.GetValue(TInput input)
   at System.Data.Entity.Internal.LazyInternalContext.InitializeContext()
   at System.Data.Entity.Internal.InternalContext.Initialize()
   at System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type entityType)
   at System.Data.Entity.Internal.Linq.InternalSet`1.Initialize()
   at System.Data.Entity.Internal.Linq.InternalSet`1.Include(String path)
   at System.Data.Entity.Infrastructure.DbQuery`1.Include(String path)
   at System.Data.Entity.QueryableExtensions.Include[T](IQueryable`1 source, String path)
   at System.Data.Entity.QueryableExtensions.Include[T,TProperty](IQueryable`1 source, Expression`1 path)
   at Jotihunt.Data.DataAccess.MapData.GetCars() in C:\SourceControl\BitBucket\Jotihunt\Data.DataAccess\MapData.cs:line 117
   at Jotihunt.Business.Logic.CarFacade.GetAll() in C:\SourceControl\BitBucket\Jotihunt\Business.Logic\CarFacade.cs:line 30
   at Jotihunt.Presentation.Web.Api.CarController.Get() in C:\SourceControl\BitBucket\Jotihunt\Jotihunt.Presentation.Web\Api\CarController.cs:line 21
   at lambda_method(Closure , Object , Object[] )
   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass13.<GetExecutor>b__c(Object instance, Object[] methodParameters)
   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.Execute(Object instance, Object[] arguments)
   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.<>c__DisplayClass5.<ExecuteAsync>b__4()
   at System.Threading.Tasks.TaskHelpers.RunSynchronously[TResult](Func`1 func, CancellationToken cancellationToken)

我嘗試了這個問題中的建議： Add-Migration not working with MySQL Unfortunatly that didn't work..

Answer 1

確保以下軟件具有相同的版本：

MySQL Connector/NET
MySql.Data/MySql.Data.Entity/MySql.Data.EntityFrameworks

當有人像我一樣用谷歌搜索這個線程時，這可能會有所幫助。