entity-framework-4 model-view-controller

预加载在 EF 中不起作用

发布于 2025-01-06 22:30:38 字数 726 浏览 2 评论 0原文

我正在拔头发，我不知道为什么我无法返回 AdPhotos 和 Location 实体。我正在使用 .ToList() 是否应该保持 AdPhotos 集合完好无损？

当我在返回上放置断点时，我可以看到 AdPhotos 和 Location 中的数据，但之后它就消失了。

public List<AdListing> LatestAdListings()
{
    using (var db = new AdultdirectoryEntities())
    {
        var results = (from a in db.AdListings.Include("AdPhotos").Include("Location")
                       join l in db.Locations on a.LocationID equals l.LocationID
                       where a.Approved && l.CountryID == Constants.ItemKeys.UsCountryId && a.AdPhotos.Count > 0
                       orderby a.CreateDateTime descending
                       select a).Take(5).ToList();

        return results;
    }
}

原文

I am pulling out my hair, I have no idea why I can't return the AdPhotos and Location entities. I am using .ToList() shouldn't it keep the AdPhotos collection intact?

When I place a breakpoint on the return, I can see the data in AdPhotos and Location but after that it disappears.

public List<AdListing> LatestAdListings()
{
    using (var db = new AdultdirectoryEntities())
    {
        var results = (from a in db.AdListings.Include("AdPhotos").Include("Location")
                       join l in db.Locations on a.LocationID equals l.LocationID
                       where a.Approved && l.CountryID == Constants.ItemKeys.UsCountryId && a.AdPhotos.Count > 0
                       orderby a.CreateDateTime descending
                       select a).Take(5).ToList();

        return results;
    }
}

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彩虹直至黑白 2025-01-13 22:30:38

您的 Include 调用之后是手动加入 - 不支持这种方式。一旦您使用手动连接或投影，您就会改变查询的形状，并且所有 Include 调用都会丢失。

此外，您不需要联接，因为您可以编写如下查询：

var results = (from a in db.AdListings.Include("AdPhotos").Include("Location")
               where a.Approved && a.Location.CountryID == Constants.ItemKeys.UsCountryId && a.AdPhotos.Count > 0
               orderby a.CreateDateTime descending
               select a).Take(5).ToList();

Your Include call is followed by manual join - that is not supported. Once you use manual join or projection you are changing shape of the query and all Include calls are lost.

Moreover you don't need the join because you can write the query like:

var results = (from a in db.AdListings.Include("AdPhotos").Include("Location")
               where a.Approved && a.Location.CountryID == Constants.ItemKeys.UsCountryId && a.AdPhotos.Count > 0
               orderby a.CreateDateTime descending
               select a).Take(5).ToList();

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