Группировка и суммирование строк в DataTable

   Dim restb As DataTable = CollapseDT(targetDT, "Склад,Товар", "Сумма")
 
   Public Function CollapseDT(target As DataTable, group As String, summ As String) As DataTable
        Dim returnDT As New DataTable("Collapse")
        Dim mgroups() As String = group.Split(",")
        For Each groupitem As String In mgroups
            returnDT.Columns.Add(Trim(groupitem))
        Next
        Dim msumm() As String = summ.Split(",")
        For Each summitem As String In msumm
            returnDT.Columns.Add(Trim(summitem))
        Next
 
        For Each row As DataRow In target.Rows
            If row.RowState = DataRowState.Deleted Then
                Continue For
            End If
            Dim find As Integer = 0
            Dim findrow As DataRow = Nothing
            For Each row2 As DataRow In returnDT.Rows
                find = 0
                For Each groupitem As String In mgroups
                    If row2(groupitem) = row(groupitem) Then
                        If find = 0 Then
                            find = 1
                        End If
                    Else
                        find = 2
                    End If
                Next
                If find = 1 Then
                    findrow = row2
                    Exit For
                End If
            Next
            If find = 1 Then
                For Each summitem As String In msumm
                    findrow(summitem) += row(summitem)
                Next
            Else
                findrow = returnDT.NewRow
                For Each groupitem As String In mgroups
                    findrow(groupitem) = row(groupitem)
                Next
                For Each summitem As String In msumm
                    findrow(summitem) = row(summitem)
                Next
                returnDT.Rows.Add(findrow)
            End If
        Next
        Return returnDT
    End Function

Dim ProductDT As DataTable = DS.Tables(tbProd)
Dim rr = From prod In ProductDT Group prod By prod!CategoryID Into catGR = Group Select CategoryID, csum = catGR.Sum(Function(p) CDbl(p!UnitPrice))
DataGridView2.DataSource = rr.ToArray

Dim rr = From prod In ProductDT Group prod By prod!CategoryID, prod!SupplierID Into catGR = Group Select CategoryID, SupplierID, csum = catGR.Sum(Function(p) CDbl(p!UnitPrice))
DataGridView2.DataSource = rr.ToArray