Question

The documentation has an example about grouping on multiple properties:

Dim custRegionQuery = From cust In db.Customers _
    Group cust.ContactName By Key = New With _
        {cust.City, cust.Region} Into grouping = Group

For Each grp In custRegionQuery
    Console.WriteLine(vbNewLine & "Location Key: {0}", grp.Key)
    For Each listing In grp.grouping
        Console.WriteLine(vbTab & "{0}", listing)
    Next
Next

Suppose I have a real type (i.e. not anonymous) that has properties for each element of the key, as well as a property for the group, so something a little like:

Public Class CustomerRegionGroup

    Public Sub New(city As String, region as String, customers As IEnumerable(Of Customer))
        Me.City = city
        Me.Region = region
        Me.Customers = customers
    End Sub

    Public Property City As String
    Public Property Region As String
    Public Property Customers As IEnumerable(Of Customer)
End Class

Is it possible to rewrite the original query to just return IEnumerable(Of CustomerRegionGroup), or do I have to use the anonymous type, and run a second query on the result of the first?

Answer 1

Turns out it was a lot simpler than some of the things I’d tried, as I didn’t appreciate that you could just do:

Dim custRegionQuery = From cust In db.Customers _
                      Group By cust.City, cust.Region _
                      Into Group _
                      Select New CustomerRegionGroup(City, Region, Group)