如何优化此EF查询并实现分页？

Question

I have about 14,000 rows of data. If use the following EF query, its a long time to load because I suspect it is loading all 14,000 rows and only then is any additional filtering done. This is my Select method in my repository.

Public Function SelectAll() As IEnumerable(Of be_Posts) Implements IPostRepository.SelectAll
       Dim posts As IEnumerable(Of be_Posts)
       Using db As Ctx = New Ctx
           posts = db.be_Posts.OrderByDescending(Function(x) x.DateCreated).ToList
           Return posts
       End Using

And Controller:

Function Index(page As Integer?) As ActionResult
        Dim PageSize = System.Web.Configuration.WebConfigurationManager.AppSettings("PageSize")
        Dim pageNumber As Integer = If(page, 1)
        Dim posts = _repo.SelectAll()
        Return View(posts.ToPagedList(pageNumber, PageSize))
    End Function

Helper in View:

@Html.PagedListPager((Model), Function(page) Url.Action("Index", New With { _
       .page = page _
        }), PagedListRenderOptions.ClassicPlusFirstAndLast)

Now If add in a take clause, for example .Take(500) then things are dramatically faster. How can I make this query faster and still work will all the records? I am also using Troy Goode's PagedList extension to get paging functionality. Everything is fine as long as i get just a few hundred records. So what to do? Most if not all examples of paging that I can find that use Troy's library involve all the code directly in the controller.

Answer 1

Calling ToList executes the query and, as you say, it's getting every record. Paging is done using Skip and Take , eg

Dim page = list.Skip(pageSize * (pageNumber - 1)).Take(pageSize)

The source list can be the table itself or the result of a Where or OrderBy call or whatever. Just make sure that ToList or, preferably, ToArray is called last.