how to perform groupby in linq on DataTable inside vb code?

Question

How do I perform group in LINQ inside vb code (dot.net v4.0) with DataTable and sum on the group?

In the sample below I need to add group by GroupName, ProductName and perform sum on QTY. The columns, order and where should remain as in sample, I just need to add the group and sum. The format should remain the same (getting row using e("FieldName")).

Dim ordersTable As DataTable = _dsProd.Tables("tblProductSummary")
Dim query =
         (From e In ordersTable
          Where (e("Type").ToString() = "1" Or IsDBNull(e("Type")))
          Order By e("GroupSortOrder") Ascending, e("ProductName")
          Select
            GroupName = e("GroupName"),
            ProductName = e("ProductName"),
            QTY = e("QTY"),
            Type= e("Type")
          )

Answer 1

Dim query =
         (From e In ordersTable
          Where (e("Type").ToString() = "1" Or IsDBNull(e("Type")))
          Order By e("GroupSortOrder") Ascending, e("ProductName")
          Group e By Key = New With {
              .ProductName = e("ProductName"),
              .GroupName = e("GroupName")
          } Into Group
          Select New With {
              .ProductName = Key.ProductName,
              .GroupName = Key.GroupName,
              .Sum = Group.Sum(Function(x) x("QTY"))
          })