Grouping a generic list by 2 values and concatenation from a single dataset via LINQ in VB.NET

Definition of my Class

    Public Class ProcessAlert
       Public LoanNumber As String
       Public EmailAddress As String
       Public AlertType As String
       Public AlertMethodID As Byte
    End Class

A generic list that is representative of data returned from DB

     Dim a As New List(Of ProcessAlert)

     a.Add(New ProcessAlert("0000112367", "5551110000@txt.att.net", "Alert", 2))
     a.Add(New ProcessAlert(开发者_C百科"0000112367", "5551110000@txt.att.net", "Document", 2))
     a.Add(New ProcessAlert("0000112367", "5551110000@txt.att.net", "Note", 2))
     a.Add(New ProcessAlert("0000112367", "jdoe@home.com", "Alert", 1))
     a.Add(New ProcessAlert("0000112367", "jdoe@home.com", "Document", 1))
     a.Add(New ProcessAlert("0000112367", "jdoe@home.com", "Note", 1))

     Return a

I managed this LINQ statement that will group by LoanNumber and EmailAddress but I can't get the AlertType to show up as a concatenated field of all 3 values

     Dim res = Alerts.GroupBy(Function(g) New With {Key .A = g.LoanNumber, Key .B = g.EmailAddress}) 

This code will give me a grouping by EmailAddress and the values I need of: "jdoe@home.com", "Alert, Document, Note" "5551110000@txt.att.net", "Alert, Document, Note"

    Dim res = Alerts.GroupBy(Function(i) i.EmailAddress).Select(Function(g) New KeyValuePair(Of String, String)(g.Key, String.Join(",", g.Select(Function(x) x.AlertType).ToArray())))

But I cannot seem to get the statement give me a return that looks like this:

    "0000112367","jdoe@home.com", "Alert, Document, Note"
    "0000112367","5551112222@txt.att.net", "Alert, Document, Note"

How do I get 2 fields to group and then concatenate the values of AlertType into a single field???

Thanks in advance

Are you looking for something like this:

From _a In a
Group _a.AlertType By _a.LoanNumber, _a.EmailAddress Into Group
Select New With
{
    .LoanNumber = LoanNumber,
    .EmailAddress = EmailAddress,
    .AlertTypes = String.Join(", ", Group.ToArray())
}