DateTime expirationDate = DateTime.Now.AddMinutes(lockTime); System.Web.HttpCookie timeoutCookie = new System.Web.HttpCookie( SysManagerConstants.AUTH_TIMEOUT_COOKIE_KEY, expirationDate.ToLongTimeString()); timeoutCookie.Expires = expirationDate; timeoutCookie.Path = "/"; filterContext.HttpContext.Response.Cookies.Add(timeoutCookie);Under certain scenarios I'm getting an error (when I am debugging the code) that the filterContext can not be modified after it was being sent.