实体框架迁移错误 - 序列不包含元素

command:添加迁移等等-详细
error:序列不包含元素

在出现此错误之前我做了一些事情。我对代码优先模型进行了更改，但没有运行add-migration然而。然后我添加了一个 EDMX 模型来直观地发挥一个想法。我意识到 EDMX 模型弄乱了我的代码，所以我将其删除。我试着跑add-migration并得到“序列不包含元素”。我升级到 EF 5 并卸载了旧的迁移包（除了我的配置）。然后我尝试了add-migration再次，我仍然得到“序列不包含元素”。以下是错误的其余部分。

System.InvalidOperationException: Sequence contains no elements
   at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source)
   at System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.GetQualifiedTableName(XDocument model, String entitySetName)
   at System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.<FindRenamedIndependentAssociationColumns>b__ba(<>f__AnonymousType16`2 <>h__TransparentIdentifieraa)
   at System.Linq.Enumerable.<>c__DisplayClass12`3.<CombineSelectors>b__11(TSource x)
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at System.Linq.Enumerable.<ConcatIterator>d__71`1.MoveNext()
   at System.Linq.Enumerable.<ConcatIterator>d__71`1.MoveNext()
   at System.Linq.Enumerable.<DistinctIterator>d__81`1.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.Diff(XDocument sourceModel, XDocument targetModel, String connectionString)
   at System.Data.Entity.Migrations.DbMigrator.Scaffold(String migrationName, String namespace, Boolean ignoreChanges)
   at System.Data.Entity.Migrations.Design.MigrationScaffolder.Scaffold(String migrationName, Boolean ignoreChanges)
   at System.Data.Entity.Migrations.Design.ToolingFacade.ScaffoldRunner.Scaffold(MigrationScaffolder scaffolder)
   at System.Data.Entity.Migrations.Design.ToolingFacade.ScaffoldRunner.RunCore()
   at System.Data.Entity.Migrations.Design.ToolingFacade.BaseRunner.Run()
Sequence contains no elements

当尝试使用以下命令定义列的类型和大小时，我会遇到此问题DataAnnotations.

BAD:

[Column(TypeName="VARCHAR(254)")]
public string ColumnName { get; set; }

OK:

[MaxLength(254)]
[Column(TypeName="VARCHAR")]
public string ColumnName { get; set; }