control with ID 'btnUpload_Click2' could not be found for the trigger in UpdatePanel 'UpdatePanel3'.

Getting this error message

System.InvalidOperationException: A control with ID 'btnUpload_Click2' could not be found for the trigger in UpdatePanel 'UpdatePanel3'.

[InvalidOperationException: A control with ID 'btnUpload_Click2' could not be found for the trigger in UpdatePanel 'UpdatePanel3'.]
   System.Web.UI.UpdatePanelControlTrigger.FindTargetControl(Boolean searchNamingContainers) +441246

Any ideas would be appreciated

Here is the Code

<asp:UpdatePanel ID="UpdatePanel3" runat="server">
<ContentTemplate>
<<asp:LinkButton ID="LinkButton4" runat="server" CssClass="btn btn-success" OnClick="btnUpload_Click2" Width="161px">
<span class="glyphicon glyphicon-upload"></span> Upload and Resize
</asp:LinkButton>
</ContentTemplate>
<Triggers>
<asp:PostBackTrigger Controlid="btnUpload_Click2"></asp:PostBackTrigger>
</Triggers>
</asp:UpdatePanel>