Question

I have a tag object that is loaded dinamically by javascript. This tag is loaded after a jquery post:

$.post('@Url.Action("ShowCredential", "ManageCredentials")',  
    $(form).serialize(), function(url) { 
    document.getElementById("credential_preview").innerHTML = "<object id='credencial_atual' type='application/pdf' classid='clsid:CA8A9780-280D-11CF-A24D-444553540000' width='250' height='420' style='border: 1px solid'> <param name='src' value='" + url + "#navpanes=0&scrollbar=0&zoom=100%' /></object>"; 

    $("#preview_popup").show(); 
}); 

Obs: i load the form variable with my form.

In my code-behind of the action “ShowCredential” i load a pdf in byte[] and store in my user session:

[HttpPost] 
public string ShowCredential(/* the attributes to help to load the pdf */) 
{ 
    // Loading my pdf... 
    Session.User.CurrentPDF = // set the pdf loaded 

    UrlHelper urlHelper = new UrlHelper(this.ControllerContext.RequestContext); 
    string url = urlHelper.Action("GetPDF", "ManageCredentials"); 

    return url; 
}

The url is generated with the action that will return the pdf.

[HttpGet] 
public FileResult GetPDF() 
{ 
    return File(Session.User.CurrentPDF, "application/pdf"); 
} 

So, in the first time, ok, is loaded the right pdf, but in the second, third… is loaded the same pdf, why? (i checked if i pass the right params, yes i pass =))

Obs: When i post the data to load the pdf, after – in jquery return – my code call the action GetPDF in the first time, but, when i post again, the action GetPDF is not called anymore.

Answer 1

Your code seems weird. You are sending a POST AJAX request to some controller action but you don’t seem to be doing anything in the success callback with the result (dados variable). Also you seem to be calling the VisualizarCredencial action twice: once for the AJAX request and once for rendering the PDF.

You haven’t explained your intentions so I can only be guessing what you are trying to do, and my guess is that you could have 2 controller actions: once that returns the url or an id that could be used to query the second controller action that will return the pdf.

Like this:

[HttpPost]
public ActionResult VisualizarCredencial()
{
    // some id of the pdf
    return Json(new { url = Url.Action("GetPdf", "GerenciarCredenciais", new { id = "123" }) });
}

public ActionResult GetPdf(int id)
{
    byte[] pdf = ... 
    return File(pdf, "application/pdf");
}

and now on the client you could use an iframe:

var url = '@Url.Action("VisualizarCredencial", "GerenciarCredenciais")';
$.post(url, function(result) {
    $('#preview_credencial').html(
        $('<iframe/>', {
            'class': 'pdfpreview', // some CSS class to set the width and height of the preview iframe
            'src': result.url
        })
    );
});

and to avoid potential caching problems with the GepPdf action you could decorate it with a custom [NoCache] action filter.