Update panel not working inside Gridview - Asp.Net/VB.Net - asp.net

Question

When I click the image button 'imgPaymentMethod' I require the code to change the ImageUrl of the Image Button. However, nothing happens when clicked. I have also tried putting the entire gridview inside the update panel but then I get this error:
A control with ID 'imgPaymentMethod' could not be found for the
trigger in UpdatePanel 'upPnlControls'
Front End..
<asp:GridView ID="gdvItems" runat="server" AutoGenerateColumns="False"
DataKeyNames="fileID" DataSourceID="DSUploadedItems" CssClass="mGrid"
AlternatingRowStyle-CssClass="alt">
<AlternatingRowStyle CssClass="alt"></AlternatingRowStyle>
<Columns>
<asp:TemplateField visible="true" HeaderText="Price">
<ItemTemplate>
<asp:DropDownList ID="ddlBuyPrice" runat="server" AutoPostBack="True" Font-Size="11px" Height="22px" OnSelectedIndexChanged="ddlBuyPrice_SelectedIndexChanged" SelectedValue='<%# Bind("buyPrice")%>'>
<asp:ListItem Value="0.00">Select:</asp:ListItem>
</asp:DropDownList>
<asp:LinkButton visible="false" ID="lnkPaymentMethod" runat="server" CausesValidation="False"
Text='<%# Bind("acceptPaypal")%>' > /></asp:LinkButton>
<br /><br />
<asp:Label ID="lblSoldStatus" visible="false" runat="server" CausesValidation="False" Text='<%# Bind("sold") %>' />
<asp:Image ID="imgSoldStatus" alt="Sold Status" runat="server" width="100px" ImageUrl="~/files/images/icons/iconSold.png" />
<br />
<asp:UpdatePanel ID="upPnlControls" style="margin-top:0px;" runat="server" UpdateMode="Conditional" ChildrenAsTriggers="false">
<Triggers>
<asp:AsyncPostBackTrigger controlid="imgPaymentMethod" eventname="Click" />
</Triggers>
<ContentTemplate>
<asp:ImageButton visible="true" ID="imgPaymentMethod" runat="server" CausesValidation="False" width="50px" onclick="lnkPaymentMethod_Click"></asp:ImageButton>
</ContentTemplate>
</asp:UpdatePanel>
<br />
<asp:Label ID="lblDateBought" runat="server" CausesValidation="False" Text='<%# Bind("dateBought") %>' />
<asp:LinkButton ID="lnkMarkAsSold" runat="server" OnClick="markAsSold_Click" Text="Mark As Sold" Visible="true" ></asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
VB Code..
Protected Sub lnkpaymentMethod_Click(sender As Object, e As System.EventArgs)
Dim imgPaymentMethod As ImageButton = CType(sender, ImageButton)
Dim currentRow As GridViewRow = DirectCast(imgPaymentMethod.Parent.Parent, GridViewRow)
If imgPaymentMethod.ImageUrl="~/files/images/icons/paypalIcon.gif" Then
imgPaymentMethod.ImageUrl="~/files/images/icons/cashIcon.gif"
Else
imgPaymentMethod.ImageUrl="~/files/images/icons/paypalIcon.gif"
End If
End Sub

Answer 1

After discussion we had in comments, if I understood you correctly the problem here is this line:
Dim currentRow As GridViewRow = DirectCast(imgPaymentMethod.Parent.Parent, GridViewRow)
If you want to get grid view row that you click via imgPaymentMethod button, you need to use NamingContainer instead of Parent as follow:
Dim currentRow As GridViewRow = DirectCast(imgPaymentMethod.NamingContainer, GridViewRow)