Prealoder when requesting dowload

Question

I’m making a return of a pdf from a Custom ActionResult

response.ContentType = "application/pdf";
response.AddHeader("Content-Disposition", "attachment; filename=teste.pdf");

And I wonder how I could make one preloader while the server processes this download

[Edit]

As requested, the code of the link I make the download request

@Ajax.ActionLink("Print", "Report", new { id = 20 }, new AjaxOptions { 
        Confirm="Are you cure?",
        HttpMethod="GET",
        LoadingElementId="divLoading"
    })

Answer 1

Suppose you already own the preloader ready (html, css, js) and need only call and hide the same at the time of download. If you don’t have, here is an example.

You can use ajax to call his Actionresult and call his preloader ao mesmo tempo.

<script>
    $(".downloadAnexo").click(function () {
        $("#divPreloader").fadeIn();//Chama o preloader
        $.ajax({
            url: '@Url.Action("DownloadFile")?id=' + 1,//Sua ActionResult
            type: 'GET',
            success: function () {
                $("#divPreloader").hide();//Esconde o preloader em caso de sucesso
            }, error: function () {
                $("#divPreloader").hide();//Esconde o preloader em caso de erro
            }  
        });
    });
</script>

See an example on dotNetFiddle.

Edit

Using the Ajax.Actionlink you have two options Onbegin and Oncomplete. Just call the functions to show and hide the preloader. Would look like this:

@Ajax.ActionLink("Print", "Index", new { id = 20 }, new AjaxOptions
{
    Confirm = "Are you cure?",
    HttpMethod = "GET",
    LoadingElementId = "divLoading",
      OnBegin = "onAjaxBegin",//Chamo a função onAjaxBegin
    OnComplete = "onAjaxComplete"//Quando completar, chamo a função onAjaxComplete
})

And you create the functions to do what you want:

<script>
   function onAjaxBegin() {
            $('#divPreloader').fadeIn();
        }

        function onAjaxComplete() {
            $('#divPreloader').hide();
        }
    </script>