entity-framework-6.1

问题 Using EF 6.1, I want to set a foreign key to null (break the relation between two entities), without querying for either object first. Preferably, I also don't want to supply the id of the related entity (since that requires adding it to my HTML). My current code doesn't do unnecessary queries, but requires the id of the related entity: public void RemoveCurrentTeacherOfGroup(int groupId, int teacherId) { var group = new Group { Id = groupId }; var teacher = new Teacher { Id = teacherId };

问题 Using EF6 code-first migrations, I am able to successfully save models and create new migrations for them. However, my DbContext class is in a Sharp.Data project, the actual (Sql CE) database lives under the Sharp.Server project bin folder, and my models live in a Sharp.Common project. When I run add-migration -ProjectName Sharp.Data Migration3 (pointing to Sharp.Data as that is where the DbContext is), it successfully runs and identifies changes made to the models in the Sharp.Common project

问题 I am using EF 6.1 Code First and want to track history data by using a model which (simplified) looks like this: public class Customer : IHistoryData<CustomerData> { public Guid ID { get; set; } public virtual ISet<CustomerData> Versions { get; set; } } public class CustomerData : HistoricalData { public string Name { get; set; } } public interface IHistoryData<T> where T : HistoricalData { ISet<T> Versions { get; set; } } public class HistoricalData { public int VersionID { get; set; }

问题 I've tried to get the Studies property of the Department object to lazy load, but it will only load when I eagerly load it. I've added a DepartmentId to the Study class with no results, used ICollection , ISet and virtual . Public and private setters seems to make no difference (and it shouldn't). Nothing seems to work. Using EF 6.1. public class Department { private Department() {} public Department(DepartmentTitle title) { if (title == null) throw new ArgumentNullException(); this.Title =

问题 I am running into the following error while trying to migrate a database in Entity Framework. The specified association foreign key columns 'question_set_id' are invalid. The number of columns specified must match the number of primary key columns. I dropped the original primary key QuestionSetId and created a composite key relationship. The columns in the composite key relationship also map to foreign keys. I'm not sure what the issue is. Here is the associated entity. public class

问题 var sw = new Stopwatch(); sw.Start(); Database.SetInitializer(new DropCreateDatabaseIfModelChanges<ImgSimContext>()); using (var db = new ImgSimContext()) { SqlConnection.ClearAllPools(); db.Database.Initialize(force: true); sw.Stop(); Console.WriteLine("Booted in {0}ms", sw.ElapsedMilliseconds); This takes about 2 seconds, even when the database has already been created. Is there any way I can speed it up? 回答1: If you are using EF6, then it is a known issue as described here: https:/

问题 Trying to use EntityFramework.Extensions for Delete and I have a case where I get the error from the title. Here is the scenario: public class AList { [Key] public int Id { get; set; } [Column] public int XId { get; set; } } public abstract class X { [Key] public int Id { get; set; } public ICollection<AList> TheAList { get; set; } } public class Y : X { [Column("TheId")] public int? SomeId { get; set; } } public class Z : X { [Column("TheId")] public int? SomeIdZ { get; set; } } This is the

问题 I have a parent entity foo which exists in the db, I have a property bar on this entity (One to many relation). Foo is detached because its deserialized using WebApi, so I do this to foo context.Foos.AddOrUpdate(foo); Even If there is a new bar reference attached to it, it wont get saved, however it does work like this for another relation we have which is a Many to many relation. If I add a new entity to that collection it will be saved to its table and also a row is added to the relation

问题 I implemented the soft-delete pattern demonstrated by Rowan Miller during a TechEd session but I ran into an immediate problem because I am using inheritance in my Code First model. The first error was during queries because I put the IsDeleted property on my supertype (base class) but when I intercepted the query for a subtype and tried to add the filter, EF complained that there was no such property on that type. Fair enough, I moved the properties to the subtypes and that bit worked okay.

问题 I Have defined an entity class with a key, but I don,t want that key be cluster because I have another cluster index in my entity, but I received an error when I add an Index attribute to my model, Can anybody tell me that how can I define a Non-Clustered Key ???? 回答1: AFAIK it is still not possible to create non-clustered primary key fields as part of your code first configuration. However, if you are using migrations or are in a position where you are able to, see the following Entity