Question

The code below is used in a Linq to SQL solution, and is in the Load event of a form.

It works fine to display an ordered list of people’s names, and set the value member to that person’s ID.

However, I’m going to be using these ‘people’ comboboxes a lot, so I’d like to put a sub into my Utility code there is only one line in the form’s Load event.

I want to call something like: Call ComboboBoxPeople(cbo, tblTurnbackMain, ReportedByID)

The sub would begin like: Public Sub ComboboxPeople(cbo as Combobox, tbl as 'sometype', fld as 'someothertype')

What can I use as the parameter types for tbl and fld?

'-- cboReportedBy datasource
Dim LQ = (From p In TurnbackDC.vewPeopleAll, t In TurnbackDC.tblTurnbackMain
    Where p.PeopleID = t.ReportedByID
    Select p.Person, p.PeopleID).Distinct()

Dim LT = From x In LQ
    Order By x.Person
    Select x.Person, x.PeopleID

cboReportedBy.DataSource = LT
cboReportedBy.DisplayMember = "Person"
cboReportedBy.ValueMember = "PeopleID"

Thanks!
Dan

Answer 1

In your first LINQ query, you are defining an anonymous type. If you want you can put almost the whole code block (both LQ and LT) in a single method and return LT. Since LT contains an IEnumerable(Of T) with T being an anonymous type, you can let your method simply return an IEnumerable, as follows:

Public Shared Function GetAllPeople() As IEnumerable
   ' code here
End Function

This will work in ASP.NET Web Forms, since Web Forms uses reflection to load the data from members that do define (Person and PeopleID). However, this approach is a bit fragile, since there is no compile time support. Another option therefore is to define a special Class (let’s call it PersonDTO) that contains two public properties Person and PeopleID and let that method return an IEnumerable(Of PersonDTO) or even better an array of PersonDTO objects.