Question

I’m having issues implementing the TOP or SKIP functionality when building a new object query.

I can’t use eSQL because i need to use an “IN” command – which could get quite complex if I loop over the IN and add them all as “OR” parameters.

Code is below :

Using dbcontext As New DB

       Dim r As New ObjectQuery(Of recipient)("recipients", dbcontext)
        r.Include("jobs")
        r.Include("applications")

        r = r.Where(Function(w) searchAppIds.Contains(w.job.application_id))

        If Not statuses.Count = 0 Then
            r = r.Where(Function(w) statuses.Contains(w.status))
        End If

           If Not dtFrom.DbSelectedDate Is Nothing Then
                r = r.Where(Function(w) w.job.create_time >= dtDocFrom.DbSelectedDate)

            End If

            If Not dtTo.DbSelectedDate Is Nothing Then
                r = r.Where(Function(w) w.job.create_time <= dtDocTo.DbSelectedDate)

            End If

            'a lot more IF conditions to add in additional predicates

            grdResults.DataSource = r

        grdResults.DataBind()              

If I use any form of .Top or .Skip it throws an error : Query builder methods are not supported for LINQ to Entities queries

Is there any way to specify TOP or Limit using this method? I’d like to avoid a query returning 1000’s of records if possible. (it’s for a user search screen)

Answer 1

Rather than

r = new ObjectQuery<recipient>("recipients", dbContext)

try

r = dbContext.recipients.

.Skip() and .Take() return IOrderedQueriable<T> while .Where returns IQueriable<T>. Thus put the .Skip() and .Take() last.

Also change grdResults.DataSource = r to grdResults.DataSource = r.ToList() to execute the query now. That’ll also allow you to temporarily wrap this line in try/catch, which may expose a better message about why it’s erroring.