How To: show loading or progress message in website in ASP.NET

ASP.NET Display “Loading…” message while update panel is updating

You can use code as below when

using Image as Loading:

 
<asp:UpdateProgress id="updateProgress" runat="server">
     <ProgressTemplate>
            <div style="position: fixed; text-align: center; height: 100%; width: 100%; top: 0; right: 0; left: 0; z-index: 9999999; background-color: #000000; opacity: 0.7;">
                    <asp:Image ID="imgUpdateProgress" runat="server" ImageUrl="~/images/ajax-loader.gif" AlternateText="Loading ..." ToolTip="Loading ..." style="padding: 10px;position:fixed;top:45%;left:50%;" />
            </div>
     </ProgressTemplate>
</asp:UpdateProgress>

using Text as Loading:

 
 <asp:UpdateProgress id="updateProgress" runat="server">
         <ProgressTemplate>
                <div style="position: fixed; text-align: center; height: 100%; width: 100%; top: 0; right: 0; left: 0; z-index: 9999999; background-color: #000000; opacity: 0.7;">
                      <span style="border-width: 0px; position: fixed; padding: 50px; background-color: #FFFFFF; font-size: 36px; left: 40%; top: 40%;">Loading ...</span>
                </div>
         </ProgressTemplate>
    </asp:UpdateProgress>


Reference: StackOverflow.com