Question

I’ve got a page that has a button control and several links to download files. The links for the file downloads point to a generic handler, since these files are secured and they will only be returned if the user is logged in.

If I load the page and click the button without doing anything else it works fine, and the event fires. But if I click a link and download a file, the next time I click the button it simply downloads the file again, instead of firing the event.

Any help would be greatly appreciated. Thanks in advance.

Edit: Here is an example link that is generated for downloading a file. These are generated using an ASP.NET LinkButton control inside an ASP.NET repeater control.

<a id="ctl00_Content_LessonFileRepeater_ctl06_FileLinkButton" href="javascript:WebForm_DoPostBackWithOptions(new WebForm_PostBackOptions(&quot;ctl00$Content$LessonFileRepeater$ctl06$FileLinkButton&quot;, &quot;&quot;, false, &quot;&quot;, &quot;Handlers/FileDownload.ashx?id=02142fe4-12ab-43bf-82f4-5a72b604ab7b&quot;, false, true))">My File.zip</a>

Edit: Here is the code in the download handler.

public void ProcessRequest(HttpContext context)
    {
        if (!AuthenticationHelper.UserIsLoggedIn)
            RedirectToNotAuthorizedPage(context);
        string fileId = context.Request.QueryString["id"];
        if (!Regex.IsMatch(fileId, RegexConstants.Guid))
            RedirectToNotAuthorizedPage(context);
        else
        {
            var lessonFileRepository = new LessonFileRepository();
            LessonFile file = lessonFileRepository.GetById(new Guid(fileId));
            if (file == null)
                RedirectToNotAuthorizedPage(context);
            else
            {
                if (!AuthenticationHelper.CurrentUser.AuthorizedLessons.Any(i => i.LessonFiles.Any(j => j.LessonFileId == file.LessonFileId)))
                    RedirectToNotAuthorizedPage(context);
                else
                {
                    context.Response.Buffer = true;
                    context.Response.Clear();
                    string encodedFileName = context.Server.UrlEncode(file.FileName + '.' + file.FileExtension);
                    encodedFileName = encodedFileName.Replace(@"+",
                                                              context.Request.Browser.Browser == "IE"
                                                                  ? @"%20"
                                                                  : @"_");
                    context.Response.AddHeader("content-length", GetFileLength(context, file.Lesson.LessonNumber, file.FileName+"."+file.FileExtension));
                    context.Response.AddHeader("content-disposition", "attachment; filename=" + encodedFileName + ";");
                    context.Response.ContentType = "application/" + GetContentType(file.FileExtension) + ";";
                    context.Response.WriteFile("~/LessonFiles/Lesson" + file.Lesson.LessonNumber + "/" +
                                               file.FileName + '.' + file.FileExtension);
                    context.Response.End();
                }
            }
        }
    }

    protected string GetFileLength(HttpContext context, int lessonNumber, string fullFileName)
    {
        var fileData = File.OpenRead(context.Server.MapPath("~/LessonFiles/Lesson" + lessonNumber + "/" + fullFileName));
        return fileData.Length.ToString();
    }

Answer 1

Your browser is caching the request. The request is never reaching the server at all…you can check your request logs to confirm this.

To disable this, you need to add this line of code in your response:

context.Response.Cache.SetCacheability(HttpCacheability.NoCache)