The full exception is a little more verbose, but not much more helpful:

Exception calling “SetData” with “2” argument(s): “Type ‘Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.Automation.OAProject’ in assembly ‘Microsoft.VisualStudio.ProjectSystem.VS.Implementation, Version=15.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a’ is not marked as serializable.” At C:\myapp\packages\EntityFramework.6.2.0\tools\EntityFramework.psm1:722 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.UpdateDatabaseCommand.<>c__DisplayClass2.<.ctor>b__0() at System.Data.Entity.Migrations.MigrationsDomainCommand.Execute(Action command)

When does it happen?

Typically, you get it when you’re trying to do a EF operation, for example:

Update-Database

But your start-up project does not have an app.config or web.config file that has a connection string pointing to that database.

Why does it happen?

EF looks in your start-up project to find your web.config and work out where your database is. Clearly this could be a slightly better worded error.