在MVC中停止执行HTTPPOST ActionMethod

Question

I have webApplication in MVC Framework..

i have situation where i have to provide user to export some data to csv file for that i have written following code ..

   [HttpPost]
     public  ActionResult ExportReportToFile(ReportCriteriaViewModels posdata, string name)
     {
            string strQuery = GetReportQuery(posdata, name);
            IEnumerable<REP_MM_DEMOGRAPHIC_CC> lstDemographics = ReportDataAccess.GetReportData<REP_MM_DEMOGRAPHIC_CC>(strQuery);
            if (lstDemographics.Count() > 0)
                  return new CsvActionResult<REP_MM_DEMOGRAPHIC_CC>(lstDemographics.ToList(), "LISDataExport.csv");
             else
               return view(posdata);
        }

Above code works fine... if in listResult Count is Greater than zero then i returns File to download.. but if i dont get any records in lstDemographics then i returns view..

My problem is when i dont get any result in lstDemographics , i dont want to return view coz it refreshes whole view.. so is there any way where we can stop execution of Action Method and browser doesn't refresh the view and stay as it is..

Thanks..

Answer 1

You will have to make an AJAX call to stop page refresh.

To achieve file export, we actually broke the process in two AJAX calls. First call sends a request to server, server prepare a file and store it in temp table. Server return the file name to AJAX call if there is data. If no data or error, it return a JSON result to indicate a failure.

On success, view make another AJAX request to download the file passing file name.

Something like this:

    [Audit(ActionName = "ExportDriverFile")]
    public ActionResult ExportDriverFile(int searchId, string exportType, string exportFormat)
    {
        var user = GetUser();
        var driverSearchCriteria = driverSearchCriteriaService.GetDriverSearchCriteria(searchId);

        var fileName = exportType + "_" + driverSearchCriteria.SearchType + "_" + User.Identity.Name.Split('@')[0] + "." + exportFormat;
        //TempData["ExportBytes_" + fileName] = null;
        _searchService.DeleteTempStore(searchId);

        var exportBytes = exportService.ExportDriverFileStream(driverSearchCriteria, searchId, exportType, exportFormat, user.DownloadCode, user.OrganizationId);
        if (exportBytes != null)
        {
            var tempStore = new TempStore
            {
                SearchId = searchId,
                FileName = fileName,
                ExportFormat = exportFormat,
                ExportType = exportType,
                DataAsBlob = exportBytes
            };

            var obj = _searchService.AddTempStore(tempStore);
            return Json(fileName);
        }
        else
        {
            return Json("failed");
        }
    }

    [HttpGet]
    public ActionResult DownloadStream(string fileName, int searchId)
    {
        var tempStore = _searchService.GetTempStore(searchId);
        var bytes = tempStore.DataAsBlob;
        if (bytes != null)
        {
            var stream = new MemoryStream(bytes);
           // TempData["ExportBytes_" + fileName] = null;
            _searchService.DeleteTempStore(searchId);
            return File(stream, "application/vnd.ms-excel", fileName);
        }

        _logger.Log("Export/DownloadStream request failed", LogCategory.Error);
        return Json("Failed");
    }

At client side, we do something like:

    function ExportData(exportType, exportFormat) {

        var searchId = document.getElementById('hfSelectedDriverId').value;
        var model = { searchId: searchId, exportType: exportType, exportFormat: exportFormat };
        //$('div[class=ajax_overlay]').remove();
        //alert("The file will be downloaded in few minutes..");

        $.ajax({
            url: '@Url.Action("ExportDriverFile", "Export")',
            contentType: 'application/json; charset=utf-8',
            type: 'POST',
            dataType: 'html',
            data: JSON.stringify(model)
        })
            .success(function (result) {
                result = result.toString().replace(/"/gi, "");
                if (result == "" || result == "failed")
                {
                    alert("File download failed. Please try again!");
                }
                else
                {
                    window.location = '/Export/DownloadStream?fileName=' + result+"&searchId="+searchId;
                }
            })
        .error(function (xhr, status) {
            //
            //alert(status);
        });

        //$('div[class=ajax_overlay]').remove();
    }

Answer 2

You should create javascript function with $.getJSON method. On controller side you just have to check, if you get data from database then return file path else return message.

Your JS code should be something like this:

                $.getJSON(url)
                    .done(function (data) {
                        if (data.filePath) // If get data, fill filePath
                            window.location = data.filePath;
                        else
                            alert(data.msg);
                    });

And from controller you can create a HTTPGET Action method that return JSON data like:

return Json(new { msg = "No data found" }, JsonRequestBehavior.AllowGet);

Based on condition you can simple change msg with filePath.