实体对象不能由IEntityChangeTracker的多个实例中的通用信息库所引用 [英] Entity object cannot be referenced by multiple instances of IEntityChangeTracker in a generic repository

问题描述

我使用了一个通用接口和存储库在这个<一个href=\"http://www.tugberkugurlu.com/archive/generic-repository-pattern-entity-framework-asp-net-mvc-and-unit-testing-triangle\"相对=nofollow> tugberkugurlu ，这是...

i have used a generic interface and repository in this tugberkugurlu, which is...

public interface IGenericRepository<T> where T : class {

    IQueryable<T> GetAll();
    IQueryable<T> FindBy(Expression<Func<T, bool>> predicate);
    void Add(T entity);
    void Delete(T entity);
    void Edit(T entity);
    void Save();
}

和这个通用库

public abstract class GenericRepository<C, T> : 
    IGenericRepository<T> where T : class where C : DbContext, new() {

    private C _entities = new C();
    public C Context {

        get { return _entities; }
        set { _entities = value; }
    }

    public virtual IQueryable<T> GetAll() {

        IQueryable<T> query = _entities.Set<T>();
        return query;
    }

    public IQueryable<T> FindBy(System.Linq.Expressions.Expression<Func<T, bool>> predicate) {

        IQueryable<T> query = _entities.Set<T>().Where(predicate);
        return query;
    }

    public virtual void Add(T entity) {
        _entities.Set<T>().Add(entity);
    }

    public virtual void Delete(T entity) {
        _entities.Set<T>().Remove(entity);
    }

    public virtual void Edit(T entity) {
        _entities.Entry(entity).State = System.Data.EntityState.Modified;
    }

    public virtual void Save() {
        _entities.SaveChanges();
    }
}

这现在可以像这样使用...

which can now be used like this...

public class FooRepository :
    GenericRepository<FooBarEntities, Foo>, IFooRepository {

    public Foo GetSingle(int fooId) {

        var query = GetAll().FirstOrDefault(x => x.FooId == fooId);
        return query;
    }
}

现在，一切，或者是很好，直到我有一个自参考实体，像这样...

now, all is, or was well until i had a self referencing entity, like this...

public class Question
    {
        [Key]
        public string QuestionID { get; set; }

        public string QuestionNumber { get; set; }

        public string Message { get; set; }

        public DateTime? DatePosted { get; set; }

        public DateTime? Modified { get; set; }

        public bool HasSubgroups { get; set; }

        public string ApplicationUserId { get; set; }
        [ForeignKey("ApplicationUserId")]
        public virtual ApplicationUser ApplicationUser { get; set; }

        public string PaperID { get; set; }
        [ForeignKey("PaperID")]
        public virtual PaperEntity Paper { get; set; }

        public ICollection<QuestionTag> Tags { get; set; }

        public ICollection<QuestionVote> Votes { get; set; }

        public virtual ICollection<Answer> Answers { get; set; }

        public virtual ICollection<QuestionComment> QuestionComments { get; set; }

        public string ParentQuestionID { get; set; }
        [ForeignKey("ParentQuestionID")]
        public virtual Question QuestionReference { get; set; }
        public virtual ICollection<Question> Questions { get; set; }
    }

和，你可以看到，我的模型让我有子问题的问题。这就是我如何努力实现它......

and as you can see, my model allows me to have sub-questions to a question. and this is how i try to implement it...

dynamic model = modela;

            string q_id = model.QuestionID.ToString();

            var question = q_id.IsNullOrEmpty() ? null : await questionRepository.FindBy(id => id.QuestionID == q_id);

            if (question == null)
            {
                question = new Question
                {
                    QuestionID = Guid.NewGuid().ToString("D"),
                    QuestionNumber = model.ParentQuestionNumber,
                    PaperID = model.PaperID,
                    Message = model.QuestionTitle,
                    ApplicationUserId = userid,
                    DatePosted = DateTime.UtcNow,
                    Tags = new List<QuestionTag>()
                };

                await questionRepository.Add(question); 
            }

            var questionQuestion = new Question
            {
                QuestionID = Guid.NewGuid().ToString("D"),
                ParentQuestionID = question.QuestionID,
                QuestionNumber = model.QuestionNumber,
                PaperID = question.PaperID,
                Message = model.Message,
                ApplicationUserId = userid,
                DatePosted = DateTime.UtcNow,
                Tags = new List<QuestionTag>()

            };

question.Questions = new List<Question>{questionQuestion};

            await questionRepository.Update(question);
            await questionRepository.Save();

和我能够保存的第一个子问题之后，第二个问题在...抛出一个错误

and after i am able to save the first sub-question, the second question throws an error at...

_ctx.Entry(entity).State = EntityState.Modified;

说...

A first chance exception of type 'System.InvalidOperationException' occurred in EntityFramework.dll

Additional information: An entity object cannot be referenced by multiple instances of IEntityChangeTracker.

我甚至使用的IDisposable 在 GenericRepository 没有运气尝试......任何暗示闻援助将是非常AP preciated ...

i have even tried using IDisposable on GenericRepository without luck...Any hint smelling assistance will be highly appreciated...

推荐答案

我想ü有因为环境的问题。大概u有两种情况使用相同的实体。这可能是因为创造了上下文每库。尝试使用的UnitOfWork 格式，或者只是为所有仓库一个上下文。

I suppose u have problem because of contexts. Probably u have two contexts with the same entity. It can be because of creating context-per-repository. Try to use UnitOfWorkpattern, or just create one context for all repositories.

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