相关疑难解决方法(0)

嗨,我打算在我的一个项目中测试EF Code First.这就是我想要的.我有三张桌子,结构如下

public partial class App_user
    {
        public int id { get; set; }
        public string name { get; set; }
        public string email_address { get; set; }
        public string password { get; set; }
        public int user_type { get; set; }
        public List<Role> Roles { get; set; }
    }

public partial class Role
    {
        public int id { get; set; }
        public string name { get; set; }
    }
public partial class User_role
    {
        public int user_id { …

我发现大多数人在使用时都会遇到此错误SingleOrDefault。然而，我正在使用FirstOrDefault. 有人见过这种异常现象吗？我使用存储库模式来使用依赖注入。

return context.Users.FirstOrDefault(p => p.Username.ToLower() == username.ToLower());

编辑

参见下文：据我所知，该错误来自 EntityFramework 的内部代码。

[InvalidOperationException: Sequence contains more than one matching element]
   System.Linq.Enumerable.SingleOrDefault(IEnumerable`1 source, Func`2 predicate) +2668318
   System.Data.Entity.ModelConfiguration.Conventions.IdKeyDiscoveryConventionImpl.MatchKeyProperty(EdmEntityType entityType, IEnumerable`1 primitiveProperties) +121
   System.Data.Entity.ModelConfiguration.Conventions.KeyDiscoveryConvention.System.Data.Entity.ModelConfiguration.Conventions.IEdmConvention<System.Data.Edm.EdmEntityType>.Apply(EdmEntityType entityType, EdmModel model) +72
   System.Data.Entity.ModelConfiguration.Conventions.IdKeyDiscoveryConvention.System.Data.Entity.ModelConfiguration.Conventions.IEdmConvention<System.Data.Edm.EdmEntityType>.Apply(EdmEntityType entityType, EdmModel model) +17
   System.Data.Entity.ModelConfiguration.Configuration.EdmConventionDispatcher.Dispatch(TEdmDataModelItem item) +100
   System.Data.Entity.ModelConfiguration.Configuration.EdmConventionDispatcher.VisitEdmEntityType(EdmEntityType item) +22
   System.Data.Edm.Internal.DataModelItemVisitor.VisitCollection(IEnumerable`1 collection, Action`1 visitMethod) +138
   System.Data.Edm.Internal.EdmModelVisitor.VisitEntityTypes(EdmNamespace edmNamespace, IEnumerable`1 entityTypes) +75
   System.Data.Edm.Internal.EdmModelVisitor.VisitEdmNamespace(EdmNamespace item) +88
   System.Data.Entity.ModelConfiguration.Configuration.EdmConventionDispatcher.VisitEdmNamespace(EdmNamespace item) +31
   System.Data.Edm.Internal.DataModelItemVisitor.VisitCollection(IEnumerable`1 collection, Action`1 visitMethod) +138
   System.Data.Edm.Internal.EdmModelVisitor.VisitNamespaces(EdmModel model, IEnumerable`1 namespaces) +75
   System.Data.Edm.Internal.EdmModelVisitor.VisitEdmModel(EdmModel item) +56
   System.Data.Entity.ModelConfiguration.Configuration.EdmConventionDispatcher.VisitEdmModel(EdmModel …