取消http.get请求并还原数据

Question

I have a page where we upload a .csv file to the database. we call a web api method that reads the file and insert the data into a table. When we upload the file a popup appears with a cancel button. What I am trying to do is to cancel the file upload process if user press the cancel button. For doing that I have created a promise and calling it on click of cancel button and it is cancelling the http request but the problem that I am facing is the data that is already imported into the database stays there. For instance if we have 100 rows in the file and by the time I press cancel button 50 rows were already inserted to the database those rows stays there. I need some help in figuring out how to revert the data that is already inserted in the table. Here is the code that I am working with:

var requestPromise = $http({
  method: 'POST',
  url: mpCONFIG.apiServiceBaseUri + 'import/fileImport',
  data: formData,
  transformRequest: angular.identity,
  timeout: canceller.promise,
  headers: {
    'Content-Type': undefined
  }
});
return requestPromise.success(function(resp, status) {
    file.progress = undefined;
    if (typeof resp != 'undefined' && resp != null && resp.length > 0) {

      $rootScope.caseFileId = resp[0];
      listImportRows(1, resp[0]);
    }
  })
  .error(function(data, status) {
    $scope.waitOnLoadingFile(false);
    file.progress = undefined;
  });
};

$rootScope.cancelLoadingFile = function() {
  canceller.resolve("User Cancelled");
  $scope.waitOnLoadingFile(false);
  $window.location.reload();
}

Edit: What I found out that it is not cancelling the request at all. The initial impression of stopping at half way was not correct and was due to some other issue. So when I press the cancel button cancelLoadinfFile is called but seems like canceller.resolve is not cancelling the request. Below is the web api method.

  [Route("fileImport")]
    [HttpPost]
    public System.Threading.Tasks.Task<IHttpActionResult> UploadImage()
    {
        try
        {
            IEnumerable<Models.mlsp.Firm> firms = (from cs in User.Firms(db)
                                                   select cs);

            HttpRequestMessage request = this.Request;
            if (!request.Content.IsMimeMultipartContent())
            {
                throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.UnsupportedMediaType));
            }

            MultipartFormDataStreamProvider provider = new MultipartFormDataStreamProvider(Properties.Settings.Default.UploadTempFolder);

            string user = RequestContext.Principal.Identity.Name;

            System.Threading.Tasks.Task<IHttpActionResult> task = request.Content.ReadAsMultipartAsync(provider).
                ContinueWith<IHttpActionResult>(o =>
                {
                    System.Net.HttpStatusCode resultStatus = HttpStatusCode.OK;
                    int?[] result = new int?[provider.FileData.Count];

                    try
                    {
                        for (int i = 0; i < provider.FileData.Count; i++)
                        {
                            result[i] = Logic.mlsp.Case.LoadFromFile(User, db, provider.FileData[i].LocalFileName, firms);
                        }
                        return ResponseMessage(new HttpResponseMessage()
                        {
                            StatusCode = resultStatus,
                            Content = new StringContent(Newtonsoft.Json.JsonConvert.SerializeObject(result))
                        });
                    }
                    catch (Exception ex)
                    {
                        Helpers.LogHelper.LogError(ex);
                        throw;
                    }
                }
            );
            return task;
        }
        catch (Exception ex)
        {
            Helpers.LogHelper.LogError(ex);
            throw;
        }
    }

Answer 1

According to this link, http://www.davepaquette.com/archive/2015/07/19/cancelling-long-running-queries-in-asp-net-mvc-and-web-api.aspx , you can add a CancellationToken parameter to the controller method. When the client cancels the request the token will be canceled as well. You need to pass this token along to the task or monitor the IsCancellationRequested property as necessary.