File upload control inside Update panel

We need to use Postback triggers to upload the file.

    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate >
    // Your File upload control here
    </ContentTemplate>
        <Triggers>
            <asp:PostBackTrigger ControlID="Button1" />  // Submit Button ID
        </Triggers>
    </asp:UpdatePanel>