Linq查询返回相同的名称，即使它们不同 [英] Linq query returns the same names even though they should be different

问题描述

我是EF6的新手，我已经设置了Chinook数据库，并且在.NET Framework 4.0上使用SqlLite .NET提供程序。

当我执行以下查询，它执行没有问题，但轨道名称都是一样的。它们应该是不同的，因为它们具有不同的轨迹ID，并且我查找了这些轨道ID，并且它们具有不同的名称。

  var result = context.Playlists.Include（p => p.Tracks）
 .Where（p => p.Name ==Brazilian Music）
 .SelectMany（p => p.Tracks ）; 
 
 foreach（结果中的var p）
 {
 Console.WriteLine（p.Playlist.Name +，+ p.TrackId +，+ p.Track。名称）; 
} 
  

欣赏任何帮助。

这是我的结果的输出：

控制台输出：

解决方案

好的，我尝试了另一种方法，使用连接连接表，现在它给出正确的结果

  var result = from p in context.Playlists 
 join pt in p.PlaylistId上的context.PlaylistTracks等于pt.PlaylistId 
在上下文中加入t.trackId上的跟踪等于t.TrackId 
其中p.Name ==Brazilian Music
 select new { PlaylistName = p.Name，TrackId = t.TrackId，TrackName = t.Name}; 
 
 foreach（结果中的var p）
 {
 Console.WriteLine（p.PlaylistName +，+ p.TrackId +，+ p.TrackName）; 
} 
  

我已经检查了连接表POCO，我没有看到任何问题

我仍然不明白为什么第一种方法不起作用。

I am new to EF6 and I have set up the Chinook database and gotten it working with SqlLite .NET provider on .NET Framework 4.0.

When I execute the following query, it executes without problems but the track names are all the same. They should be different because they have different track IDs and I have looked up those track IDs and they have different names.

var result = context.Playlists.Include(p => p.Tracks)
                .Where(p => p.Name == "Brazilian Music")
                .SelectMany(p => p.Tracks);

foreach(var p in result)
{
  Console.WriteLine(p.Playlist.Name + ", " + p.TrackId + ", " + p.Track.Name);
}

Appreciate any help.

Here is the output of my result:

Console Output:

解决方案

OK, I tried another approach using joins to the junction table and now it gives the correct result

var result = from p in context.Playlists
             join pt in context.PlaylistTracks on p.PlaylistId equals pt.PlaylistId
             join t in context.Tracks on pt.TrackId equals t.TrackId
             where p.Name == "Brazilian Music"
             select new { PlaylistName = p.Name, TrackId = t.TrackId, TrackName = t.Name };

foreach (var p in result)
{
  Console.WriteLine(p.PlaylistName + ", " + p.TrackId + ", " + p.TrackName);
}

I have checked the junction table POCO and I don't see any problems with it.

I still don't understand why the first approach isn't working.

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