Datatype argument cannot be null parameter name datatype iam getting this problem while transfering data fro datagridview to other form datagridview

Try
            Dim dt2 As New DataTable

            dt2.Columns.Add("Metal", Type.GetType("system.string"))
            dt2.Columns.Add("Discription", Type.GetType("system.string"))
            dt2.Columns.Add("Huid", Type.GetType("system.string"))
            dt2.Columns.Add("Hsn", Type.GetType("system.string"))
            dt2.Columns.Add("Qty", Type.GetType("system.string"))
            dt2.Columns.Add("Unit", Type.GetType("system.string"))
            dt2.Columns.Add("GrossWt", Type.GetType("system.string"))
            dt2.Columns.Add("StoneWt", Type.GetType("system.string"))
            dt2.Columns.Add("NetWt", Type.GetType("system.string"))
            dt2.Columns.Add("Wastage", Type.GetType("system.string"))
            dt2.Columns.Add("Rate", Type.GetType("system.string"))
            dt2.Columns.Add("Mc", Type.GetType("system.string"))
            dt2.Columns.Add("Amount", Type.GetType("system.string"))


            For Each Row As DataGridViewRow In datagriditemdiscrib.Rows
                For i As Integer = 0 To datagriditemdiscrib.Rows.Count - 2 Step +1
                    dt2.Rows.Add(Row.Cells(0).Value, Row.Cells(1).Value, Row.Cells(2).Value, Row.Cells(3).Value, Row.Cells(4).Value, Row.Cells(5).Value, Row.Cells(6).Value, Row.Cells(7).Value, Row.Cells(8).Value, Row.Cells(9).Value, Row.Cells(10).Value, Row.Cells(11).Value, Row.Cells(12).Value)

                Next

            Next



        Catch ex As Exception
            MsgBox(ex.Message)
        End Try



        Invoice_print.Show()
        Invoice_print.datagriditemdiscrib_print.DataSource = dt2