using LINQ to databind unique records

Question

User-153404742 posted

I'm trying to dataBind records from a Linq Query in a gridView control.  I have a gridview inside another gridview for one of the columns.  Data displays correctly if ALL the columns are Distinct, but I need Distinct records on ALL but one of the columsn, which is the sub gridview within the main one.  I don't know how to work out LINQ query for this.  I have the following:

 Dim Activities = (From a In db.Activities _
        Join b In db.Activities_Attendees _
        On a.ActivityID Equals b.ActivityID _
        Where (a.CreatedBy = CType(Session("CID"), Integer) And (a.ActivityTime <> 0.0) And _
        (a.Date >= projyear And (a.Date <= DateAdd(DateInterval.Day, -1, DateAdd(DateInterval.Year, 1, projyear))))) _
        Select a.ActivityID, a.Type, a.ActivityTime, a.Date, a.CreatedBy, a.Comments, b.SignedDate).Distinct

        activitiesGridView.DataSource = Activities.ToList()
        activitiesGridView.DataBind()

What is happening is that the b.SignedDate can be null or have a date.  If there are two records for the same activity, where one record has a null SignedDate and the other has a date, that record shows up twice....however, I only want the record to show up once.  So I need to get distinct on all the columns of "a" table group but not on b.SignedDate.  I know I have to use group by but I'm not sure how to go about doing this....thanks for any help.

Answer 1

User753101303 posted

Hi,

And you'll want the later?  So you want all lines from "a" but only the last SignedValue found in "b". Correct?

Not directly related but I would favor navigation properties over explicit join if you can. The whole point of Linq is to write C# code that is translated for you to SQL rather than to really mimic SQL.