Question

I’m using ASP.NET and C# and am exporting a very large results set to Excel. While my export code is running I would like to show a ‘loading’ animated gif so the users will know their request is processing. I’ve been trying to do this with multithreading, but I am not very familiar with it. Can anyone guide me in the right direction? Thanks!

Jon

Answer 1

Are you trying to do multi-threading on the server? What I’d recommend is in your client side javascript turn on a please wait message before posting to the server. Then on the client side when your done posting you turn the message off.

Without knowing more about your actual setup I can’t help much further, but last time I implemented this I did something along these lines:

Assume we have a div called PrintLoadingPanel using JQUERY I set the div to display and take over the window:

    $('#printLoadingPanel')        .css({display:'block',top:'0px',left:'0px',height:screen.availHeight}); 

I then will start a timer with a 1/2 second interval which will start checking if we are done printing. I’m only generating and downloading small PDF’s so i needed a quicker response. If your report is really slow you might want to tweak this:

    window.setTimeout(checkIfDoneDownload,500); 

Then my CheckIfDoneDownload function hits the server and checks if we finished generating the file and downloaded it. I am using JQUERY here again to call an AJAX enabled WCF service. You could substitute this with PageMethods or any other way to callback to the server.

function checkIfDoneDownload() {  $.ajax({   type: 'POST',   url: '../Services/Utilities.svc/IsPrintDownloadDone',   data: '{}',   contentType: 'application/json; charset=utf-8',   dataType: 'json',   success: function(msg) {   if (msg.d)   {     $('#printLoadingPanel').css('display','none');   }   else  {window.setTimeout(checkIfDoneDownload,500);}   },     error: function (xhr, textStatus, errorThrown) {   if (xhr.status==12030) {checkIfDoneDownload();} } }); } 

Now on the server side, I am generating my downloads via an HTTP Handler. Essentially the first thing it does is set a session level flag to false, then the last thing it does is set it back to true. My check if done service just returns the value of the flag.