实体框架多对多查询 [英] Entity Framework Many to Many query

问题描述

我想写一个简单的查询，但是有一些问题. 我有2张桌子M到N:

I want to write a simple query, but there are some problems. I have 2 tables M to N:

用户->事件.

我想获取特定事件的所有用户(通过eventId获取此事件).

I want to get all users of a specific event (get this event by eventId).

public IQueryable<User> GetUsersByEventId(int eventId)
{
    IQueryable<User> query = this.Context.Users.AsQueryable();

    return query.Where(x => x.Events.SingleOrDefault(e => e.EventId == eventId)); ??
}

缺少某种东西，我不知道该怎么办，有人可以帮助我吗?非常感谢！

Something is missing and I dont know what, can someone help me? Thanks a lot !

推荐答案

如果我对您的理解正确(添加模型会有所帮助)，我认为您想要Any

If I understand you correctly (adding your models would help), I think you want Any

public IQueryable<User> GetUsersByEventId(int eventId)
{
      return Context.Users
                    .Where(u => u.Events.Any(e => e.EventId == eventId));
}

这将返回所有事件与给定ID匹配的所有用户.

This should return all users who have any event matching the given id.

注意:如果您正确设置了人际关系，则应该可以直接从活动中获取此信息.

Note: If you set up your relationships correctly, you should be able to get this directly from the Event.

public class Event
{
    ...
    public virtual ICollection<User> Users { get; set; }
}

因此，您将通过ID获取事件并访问它的用户集合.

So then, you'd get the Event by id and access it's user collection.

var evt = repo.GetEventById(id);
var users = evt.Users;

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