用linq连接表

Question

I have 4 tables:

• Topics
• RelyTopics
• TagTopics
• TagNames.

I want to execute query with join and get 2 outputs:

• join 2 tables Topics, RelyTopics
• and join 2 tables TagTopics, TagNames

both on the same view.

In the Controller I have this code:

public ActionResult Index()
{
    var query1 = from to in db.Topics 
                      join rel in db.RelyTopics  on to.IdTopic equals rel.Id
                     select new TopicAndDetails
                     {
                         Topic = to,
                         RelyTopic = rel,
                     };
    var query2 = from tag in db.TagTopics
                join na in db.TagNames on tag.IdTag equals na.IdName
                select new TopicAndDetails
                {
                    TagTopic = tag,
                    NameTag = na,
                };

    var relytopics = new TopicAndDetails(query1, query2) ; //??????

    return View(relytopics.ToList());
}

In the Model have this code:

 public partial class TopicAndDetails
{
    public Topic Topic { get; set; }
    public TagName NameTag { get; set; }

    public TagTopic TagTopic { get; set; }
    public RelyTopic RelyTopic { get; set; }
}

Answer 1

Create your navigation properties first: https://msdn.microsoft.com/en-us/library/jj713564(v=vs.113).aspx , then you can do this:

public ActionResult Index()
{
  return db.Topics.Select(t=>new TopicAndDetails {Topic=t})
    .Concat(db.TagTopics.Select(tt=>new TopicAndDetails {TagTopic=tt));
}
public partial class TopicAndDetails
{
    public Topic Topic { get; set; }
    public TagTopic TagTopic { get; set; }
}

Your ViewModel would then be IQueryable<TopicAndDetails> or IEnumerable<TopicAndDetails>

Or this would make more sense probably:

public ActionResult Index()
{
  return new TopicAndDetails {
    Topics = db.Topics.ToList(),
    TagTopics = db.TagTopics.ToList()
  };
}
public partial class TopicAndDetails
{
    public List<Topic> Topics { get; set; }
    public List<TagTopic> TagTopics { get; set; }
}