的EntityFramework到JSON解决方法吗？ （而序列化类型的对象时检测到循环引用... DynamicProxies） [英] EntityFramework to Json workaround? ( A circular reference was detected while serializing an object of type...DynamicProxies)

问题描述

因此​​，继承人的处理我有

so heres the deal i have

模式

public class News
{

    public News()
    {
        this.Created = DateTime.Now;
    }

    public int Id { get; set; }       
    public string Title { get; set; }
    public string Preamble { get; set; }
    public string Body { get; set; }
    public DateTime Created { get; set; }

    public int UserId { get; set; }

    public virtual User User { get; set; }

    public int CategoryId { get; set; }
    public int ImageId { get; set; }

    public virtual Image Image { get; set; }
    public virtual Category Category { get; set; }
}

public class Image
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string ImageUrl { get; set; }
    public Byte[] ImageData { get; set; }
    public string ImageMimeType { get; set; }
}

public class Category
{
    public int Id { get; set; }
    public string Name { get; set; }
}

....以下型号连接到下面的仓库（这些车型都连接到EfDbContext）...

....following models(these models are connected to the EfDbContext) connected to following repository...

接口/库

public class NewsRepository : INewsRepository
{
    EfDbContext context = new EfDbContext();

    public IQueryable<News> All
    {
        get { return context.News; }
    }

    public IQueryable<News> AllIncluding(params Expression<Func<News, object>>[] includeProperties)
    {
        IQueryable<News> query = context.News;
        foreach (var includeProperty in includeProperties) {
            query = query.Include(includeProperty);
        }
        return query;
    }

    public News Find(int id)
    {
        return context.News.Find(id);
    }

    public void InsertOrUpdate(News news)
    {
        if (news.Id == default(int)) {
            // New entity
            context.News.Add(news);
        } else {
            // Existing entity
            context.Entry(news).State = EntityState.Modified;
        }
    }

    public void Delete(int id)
    {
        var news = context.News.Find(id);
        context.News.Remove(news);
    }

    public void Save()
    {
        context.SaveChanges();
    }
}

public interface INewsRepository
{
    IQueryable<News> All { get; }
    IQueryable<News> AllIncluding(params Expression<Func<News, object>>[] includeProperties);
    News Find(int id);
    void InsertOrUpdate(News news);
    void Delete(int id);
    void Save();
}

在我的HomeController（）我得到了一个JsonResult梅托德，我要返回的上下文。
这里是法

In my HomeController() i got a a JsonResult metod that i want to return the context. Here is the Method

JSON请求

    [HttpGet]
    public JsonResult GetNews()
    {
        var p = newsRepository.AllIncluding(news => news.Category, news => news.Image);
        return Json(p, JsonRequestBehavior.AllowGet);
    }

我收到以下错误：

I get the following error:

在序列化类型的对象时检测到循环引用'System.Data.Entity.DynamicProxies.News_96C0B16EC4AC46070505EEC7537EF3C68EE6CE5FC3C7D8EBB793B2CF9BD391B3'.

我猜这事做的惰性加载的东西（IAM目前学习C＃）我发现这篇文章这个...

I guessed that this has something to do with the lazyloading stuff(Iam currently learning about C#) i found this article about this...

<一个href=\"http://hellowebapps.com/2010-09-26/producing-json-from-entity-framework-4-0-generated-classes/\">http://hellowebapps.com/2010-09-26/producing-json-from-entity-framework-4-0-generated-classes/

但我没有得到它的工作...我可以阅读有关code的，他们试着深度搜索槽的对象......不止这些我无法弄清楚。

but i didnt get it to work... what i could read about the code was that they were tryin to depth search trough the object... more than that i couldn't figure out.

我的问题是如何，我可以在惰性加载的对象传递？成JSON /串行
或者它不存在，怎么我可以进行什么想法？

my question is how to i can pass in lazyLoading objects? into json/serializer or does it not exist, any thoughts of how i can proceed?

推荐答案

由于JSON是基于树的序列化格式，它具有像A-> B-> A引用的问题。结果
我读过的地方，你可以使用<一个href=\"http://msdn.microsoft.com/en-us/library/system.web.script.serialization.scriptignoreattribute.aspx\">ScriptIgnore在你的ViewModels归因于prevent此错误。但没有测试过。

Since Json is a tree-based serialization format, it has problems with references like A->B->A.
I've read somewhere that you can use ScriptIgnore attribute in your viewmodels to prevent this error. But have not tested it.

您可以更改code以下（使用匿名类型）成功地检索项目：

You can change your code to the following (use anonymous types) to retrieve the items successfully:

 var p = newsRepository.AllIncluding(news => news.Category, news => news.Image)
    .Select(n => new {id = n.Id, Body = n.Body});

包含要在最后一个选择方法来显示所有的其他财产。这使得您的JSON结果更为轻巧了。

Include any other property you wish to display in the last Select method. This makes your Json results more lightweight too.

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