Partial Class DataCollection
    Inherits System.Web.UI.Page

    Protected Sub btnAdd_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAdd.Click
        Dim Cart As DataSet = RetrieveCart()

        Cart = DumpCart(Cart)
        Dim aRow As DataRow

        aRow = Cart.Tables(0).NewRow

        ' Validation here

        aRow("SID") = StudentID.Text
        aRow("M") = Mark.Text

        Cart.Tables(0).Rows.Add(aRow)

        MarkList.DataSource = Cart.Tables(0)
        MarkList.DataBind()
    End Sub
    Private Function RetrieveCart() As DataSet
        Dim Cart As New DataSet

        Dim CartTable As New DataTable
        CartTable.Columns.Add("SID", GetType(Integer))
        CartTable.Columns.Add("M", GetType(Integer))

        CartTable.TableName = "CartTable"
        Cart.Tables.Add(CartTable)
        Cart.DataSetName = "Cart"

        Return Cart
    End Function

    Private Function DumpCart(ByVal Cart As DataSet) As DataSet
        If MarkList.Rows.Count > 0 Then

            Dim NM_TextBox As TextBox

            Dim aRow As DataRow

            For Each gRow As GridViewRow In MarkList.Rows
                aRow = Cart.Tables(0).NewRow
                aRow(0) = gRow.Cells(0).Text
                aRow(1) = gRow.Cells(1).Text
                NM_TextBox = CType(gRow.FindControl("NM"), TextBox)

                If Not (NM_TextBox Is Nothing) Then
                    If NM_TextBox.Text.Trim.Length > 0 AndAlso IsNumeric(NM_TextBox.Text.Trim) Then
                        aRow(1) = NM_TextBox.Text.Trim
                    Else
                        aRow(1) = gRow.Cells(1).Text
                        FormMessage.Text = "The new mark must be numeric "
                    End If
                End If
                Cart.Tables(0).Rows.Add(aRow)
            Next
        End If

        Return Cart
    End Function

    Protected Sub btnEdit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnEdit.Click
        Dim Cart As DataSet = RetrieveCart()
        Cart = DumpCart(Cart)
        MarkList.DataSource = Cart.Tables(0)
        MarkList.DataBind()
    End Sub
End Class