>>>select field1, sum(field2) as total from mytable group by field1
>
>Is mytable a datatable?
>Is it in a typed.dataset?

a datatable, extracted via a query on an access database (that's what oSql does, it fills osql.dt from the qryBestelKK)

        Dim osql As New sqlClass : osql.Execute("qryBestelKK")
        Dim orders As IEnumerable(Of DataRow) = osql.dt.AsEnumerable

        Dim test = From r In orders _
                   Group r By name = r.Field(Of String)("KL_Naam") _
                   Into g = Group Select New With {.Name = name, .total = g.Sum(Function(r) r.Field(Of Decimal)("Bestd_Waarde"))}

        For Each r In test
            Console.WriteLine("name: {0} total {1}", r.Name, r.total)
        Next

essentially copied it from

' Fill the DataSet.
Dim ds As New DataSet()
ds.Locale = CultureInfo.InvariantCulture
' See the FillDataSet method in the Loading Data Into a DataSet topic.
FillDataSet(ds)

Dim products As IEnumerable(Of DataRow) = _
    ds.Tables("Product").AsEnumerable()

Dim query = _
    From product In products _
    Group product By style = product.Field(Of String)("Style") Into g = Group _
    Select New With _
        { _
            .Style = style, _
            .AverageListPrice = g.Average(Function(product) _
                    product.Field(Of Decimal)("ListPrice")) _
        }

For Each product In query
    Console.WriteLine("Product style: {0} Average list price: {1}", _
        product.Style, product.AverageListPrice)
Next

Not sure I understand it, but it does work. :)

http://msdn.microsoft.com/en-us/library/bb386991.aspx

Thanks for caring and kind regards,

Marc