问题
I have a new ASP.net 5 dnx class library I am using for entity framework. I need to target EF 6 because some features I need are not in EF 7.
First the EF tools (like enable-migration) were not there. I added an old style class library and installed EF 6 and now the commands are there.
When I run enable migrations I get this error:
PM> Enable-Migrations
Exception calling "SetData" with "2" argument(s): "Type 'Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.Automation.OAProject' in assembly 'Microsoft.VisualStudio.ProjectSystem.VS.Implementation, Version=14.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' is not marked as serializable." At D:\Projects\Rebus\FMS\Code\Current\FMSSupport\FMSSupport\packages\EntityFramework.6.1.3\tools\EntityFramework.psm1:720 char:5 + $domain.SetData('startUpProject', $startUpProject) + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : NotSpecified: (:) [], MethodInvocationException + FullyQualifiedErrorId : SerializationException System.NullReferenceException: Object reference not set to an instance of an object. at System.Data.Entity.Migrations.Extensions.ProjectExtensions.GetProjectTypes(Project project, Int32 shellVersion) at System.Data.Entity.Migrations.Extensions.ProjectExtensions.IsWebProject(Project project) at System.Data.Entity.Migrations.MigrationsDomainCommand.GetFacade(String configurationTypeName, Boolean useContextWorkingDirectory) at System.Data.Entity.Migrations.EnableMigrationsCommand.FindContextToEnable(String contextTypeName) at System.Data.Entity.Migrations.EnableMigrationsCommand.<>c__DisplayClass2.<.ctor>b__0() at System.Data.Entity.Migrations.MigrationsDomainCommand.Execute(Action command) Object reference not set to an instance of an object.
I have tried different options for enable-migration such as specifying a startup project or the contextTypeName.
Any ideas?
回答1:
Following this recommendation, EF6 data projects should use the existing .NET Framework class library csproj type.
Even after following the recommendations, I was still getting the same error. Unloading your ASP.NET Core project(s) and then invoking the Enable-Migrations command on the appropriate csproj should allow the command to execute. You can unload a project by right-clicking on the .NET Core project and choosing the 'Unload Project' option. It should also be noted that the Package Manager Console window has a 'Default project:' drop-down selection. You should choose the project with your DbContext.
回答2:
It's because ASP.NET Core introduced a new project type/configuration system (see package.config vs project.json) and the old EF tools don't know how to work with the newer system (project.json). It would probably be easiest to create a new project and port your code into it if you want to go back to EF6.
Interestingly (well, disappointingly actually) they're backtracking on project.json see: http://xoofx.com/blog/2016/05/11/goodbye-project-json/
回答3:
I had the same issue. Just setting the start project from ASP.NET Core to my .NET Framework Lib does the trick for me =) Now i can do EF6 migrations as usual "Add-Migration" command...
P.S. Sorry for my eng.
来源：https://stackoverflow.com/questions/34956083/ef-6-with-a-dnx-project