my code for the above GridView (ID: "CartGrid") is as following:
Code:
<asp:GridView ID="CartGrid" runat="server" AutoGenerateColumns="False" CssClass="body_normal"
    DataKeyNames="ProductID" Width="600px" BorderColor="White" BorderWidth="1px" CellPadding="0">
    <Columns>
                <asp:TemplateField>
                    <ItemTemplate>
                    <table border="0" cellpadding="0" cellspacing="0" width="120">
                        <tr>
                        <td>
                        <asp:Image ID="Image1" runat="server" ImageUrl='<%# Eval("ProductImageUrl","images/catalog/{0}") %>' BorderColor="Silver" BorderStyle="Dotted" BorderWidth="1px" /></td>
                        </tr>
                        <tr>
                        </tr>
                        <tr>
                        </tr>
                    </table>
                    <asp:HiddenField ID="HiddenField1" runat="server" Value='<%# Eval("OriginalQty") %>' ></asp:HiddenField>
                    </ItemTemplate>   
                </asp:TemplateField>
                
                <asp:BoundField DataField="ProductName" HeaderText="Product" ReadOnly="True" />
                
                <asp:TemplateField HeaderText="Quantity">
                    <ItemTemplate>
                        <asp:Label ID="Qty1" runat="server" Text='<%# Eval("Quantity") %>' CssClass="product_normal1">
                        </asp:Label>
                    </ItemTemplate>   
                    <EditItemTemplate>
                        <asp:DropDownList ID="DropDownList1" runat="server"/>
                    </EditItemTemplate>
                </asp:TemplateField>
                
                <asp:BoundField DataField="Price" DataFormatString="{0:c}" HeaderText="Price" ReadOnly="True" />
                <asp:BoundField DataField="LineTotal" DataFormatString="{0:c}" HeaderText="Total" ReadOnly="True" />
                <asp:CommandField ShowDeleteButton="True" ShowEditButton="True" ><ItemStyle CssClass="product_link" />
                </asp:CommandField>
 
    </Columns>
</asp:GridView>
The highlighted code each represents each cell.
In my RowEditing code

I tried to access the DropDownList1 which can be found in the EditItemTemplate tag for the third cell by using the following code:

Code:
Dim rowIdx As Integer
        rowIdx = Convert.ToInt32(e.NewEditIndex.ToString)

Dim QuantityTextBox As DropDownList
        QuantityTextBox = CartGrid.Rows(rowIdx).Cells(2).FindControl("DropDownList1")
but it fails with an NullReferenceException.
Please guide, any FindControl Expert?