ASP MVC5 LINQ Multiple Selects with Lists

Question

I am writing a simple community Plugin and now I wanted to improve my db queries but run into an blocking isse:

this is the query:

TRDCommunityViewModel community = await _db.Communities
  .Select(c => new TRDCommunityViewModel
   {
    Id = c.Id,
    CommunityId = c.Guid,
    Created = c.Created,
    Description = c.Description,
    IAmAdmin = (c.Admins.FirstOrDefault(k => k.Id == userId) != null),
    Members = c.Members.Select(a => new List<TRDIdenityViewModel>()
      {
        // member vars of TRDIdenityViewModel arn't accessible
        // ???
      }),
    Posts = c.Posts.Select(a => new List<TRDIdenityViewModel>()
      {
        //member vars of TRDIdenityViewModel arn't accessible
      })
        // and so on
    })
   .FirstOrDefaultAsync(k => k.Id == Id);

My question is...how is it possible to query for related lists? Members and Posts are ICollections

Thx for helping.

Brian Driscoll · Accepted Answer · 2014-12-10 18:05:08Z

1

You should not need to instantiate a List within the Select, this should work:

TRDCommunityViewModel community = await _db.Communities
  .Select(c => new TRDCommunityViewModel
   {
    Id = c.Id,
    CommunityId = c.Guid,
    Created = c.Created,
    Description = c.Description,
    IAmAdmin = (c.Admins.FirstOrDefault(k => k.Id == userId) != null),
    Members = c.Members.Select(a => new TRDIdenityViewModel()
      {
        // do your assignments here...
      }),
    Posts = c.Posts.Select(a => new TRDIdenityViewModel()
      {
        //do your assignments here...
      })
        // and so on
    })
   .FirstOrDefaultAsync(k => k.Id == Id);

If you need to you can materialize by calling ToList() after select, e.g.:

    Posts = c.Posts.Select(a => new TRDIdenityViewModel()
      {
        //do your assignments here...
      }).ToList()

answered Dec 10, 2014 at 18:05

Brian Driscoll

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1 Comment

creality Over a year ago

Ufff...so simple. Thx alot.

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