protected void QuestionSubmitCommentButton_OnClick(object sender, EventArgs e)
        {
            var logginedUser = HttpContext.Current.User.Identity;

            if (logginedUser.IsAuthenticated)   // only logined users can submit comment
            {
                var submitButton   = (Button)sender;
                var questionId     = int.Parse(submitButton.CommandArgument);
                var commentTextBox = (TextBox)QuestionDetailFormView.FindControl("QuestionCommentBody");

                using (var control = new QuestionController())
                {
                    control.AddComment(questionId, commentTextBox.Text);
                }

                QuestionDetailFormView.DataBind();
            }
            else
            {
                var currentUrl = HttpUtility.UrlEncode(Request.Url.PathAndQuery);
                Response.Redirect($"~/Login.aspx?ReturnUrl={currentUrl}");
            }
        }