C# 首先是实体框架代码的检查列表

我有两个对象ListingActivity和Activity，ListingActivities用于将活动链接到列表

这是物品

public class ListingActivity
{
    [Key]
    public int ListingActivityId { get; set; }
    public Activity Activity { get; set; }
    public Listing Listing { get; set; }
}

public class Activity
{
    [Key]
    public int ActivityId { get; set; }
    public string Name { get; set; }
    public ListingActivity ListingActivity { get; set; }
}

我想要一个清单，这样用户可以看到哪些活动已经链接到列表，然后选择那些没有链接的活动。我知道如何做用户界面和一切。但是，使用代码优先实体框架时，该查询会是什么样子呢

我已经用SQL实现了类似的功能，然后它看起来或多或少像这样（免责声明：伪SQL）

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这就是我想要的，贴在这里，它可能会在将来帮助别人

var actList = (from a in db.Activities
                           join la in db.ListingActivities on a.ActivityId equals la.Activity.ActivityId into
                               tempActivities
                           from listingActivites in tempActivities.DefaultIfEmpty()
                           select new ListingActivityItem()
                                      {
                                          ListingActivityId = listingActivites.ListingActivityId,
                                          Activity = a,
                                          Checked = listingActivites.Listing != null
                                      }).OrderBy(p=>p.Activity.Name).ToList();
            return actList;

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Activity ListingActivity

1:n吗？

var actList = (from a in db.Activities
                           join la in db.ListingActivities on a.ActivityId equals la.Activity.ActivityId into
                               tempActivities
                           from listingActivites in tempActivities.DefaultIfEmpty()
                           select new ListingActivityItem()
                                      {
                                          ListingActivityId = listingActivites.ListingActivityId,
                                          Activity = a,
                                          Checked = listingActivites.Listing != null
                                      }).OrderBy(p=>p.Activity.Name).ToList();
            return actList;