What is wrong with this:

Label

lblcost = (Label)gv_sku_details.FindControl("lblCost");
TextBox txtcost = (TextBox)gv_sku_details.FindControl("txtCost");

decimal lcost = decimal.Parse(lblcost.Text);
decimal dcost = decimal.Parse(txtcost.Text);

///////////////////////////////////////

I get this error when i call my method

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Line 142:        decimal lcost = decimal.Parse(lblcost.Text);
Line 143:        decimal dcost = decimal.Parse(txtcost.Text);

And here is my ASPX code:

<asp:TemplateField HeaderText="COST">
<ItemTemplate>
<asp:Label ID="lblCost" runat="server" Text='<%# Bind("tot_cost") %>'></asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:Label ID="lblCost" runat="server" Text='<%# Bind("tot_cost") %>' Visible="false"></asp:Label>
<asp:TextBox ID="txtCost" runat="server" Text='<%# Bind("tot_cost") %>' CssClass="BorderedTextBox" Width="80"></asp:TextBox>
</EditItemTemplate>
</asp:TemplateField>