// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.IO;
using System.Linq.Expressions;
using System.Security.Claims;
using System.Text;
using System.Threading.Tasks;
using Microsoft.AspNet.Http;
using Microsoft.AspNet.Mvc.ModelBinding;
using Microsoft.AspNet.Mvc.ModelBinding.Validation;
using Microsoft.AspNet.Mvc.Rendering;
using Microsoft.AspNet.Mvc.ViewFeatures;
using Microsoft.AspNet.Routing;
using Microsoft.Framework.Internal;
using Microsoft.Net.Http.Headers;
using Newtonsoft.Json;

namespace Microsoft.AspNet.Mvc
{
    /// <summary>
    /// Base class for an MVC controller.
    /// </summary>
    public abstract class Controller : IActionFilter, IAsyncActionFilter, IDisposable
    {
        private DynamicViewData _viewBag;
        private ViewDataDictionary _viewData;
        private ActionContext _actionContext;

        /// <summary>
        /// Gets the request-specific <see cref="IServiceProvider"/>.
        /// </summary>
        public IServiceProvider Resolver
        {
            get
            {
                return ActionContext?.HttpContext?.RequestServices;
            }
        }

        /// <summary>
        /// Gets the <see cref="HttpContext"/> for the executing action.
        /// </summary>
        public HttpContext Context
        {
            get
            {
                return ActionContext?.HttpContext;
            }
        }

        /// <summary>
        /// Gets the <see cref="HttpRequest"/> for the executing action.
        /// </summary>
        public HttpRequest Request
        {
            get
            {
                return ActionContext?.HttpContext?.Request;
            }
        }

        /// <summary>
        /// Gets the <see cref="HttpResponse"/> for the executing action.
        /// </summary>
        public HttpResponse Response
        {
            get
            {
                return ActionContext?.HttpContext?.Response;
            }
        }

        /// <summary>
        /// Gets the <see cref="AspNet.Routing.RouteData"/> for the executing action.
        /// </summary>
        public RouteData RouteData
        {
            get
            {
                return ActionContext?.RouteData;
            }
        }

        /// <summary>
        /// Gets the <see cref="ModelStateDictionary"/> that contains the state of the model and of model-binding validation.
        /// </summary>
        public ModelStateDictionary ModelState
        {
            get
            {
                return ViewData?.ModelState;
            }
        }

        /// <summary>
        /// Gets or sets the <see cref="Mvc.ActionContext"/> object.
        /// </summary>
        /// <remarks>
        /// <see cref="IControllerActivator"/> activates this property while activating controllers. If user codes
        /// directly instantiate controllers, the getter returns an empty <see cref="Mvc.ActionContext"/>.
        /// </remarks>
        [ActionContext]
        public ActionContext ActionContext
        {
            get
            {
                // This should run only for the controller unit test scenarios
                _actionContext = _actionContext ?? new ActionContext();
                return _actionContext;
            }
            set
            {
                if (value == null)
                {
                    throw new ArgumentNullException(nameof(value));
                }

                _actionContext = value;
            }
        }

        /// <summary>
        /// Gets or sets the <see cref="ActionBindingContext"/>.
        /// </summary>
        [ActionBindingContext]
        public ActionBindingContext BindingContext { get; set; }

        /// <summary>
        /// Gets or sets the <see cref="IModelMetadataProvider"/>.
        /// </summary>
        [FromServices]
        public IModelMetadataProvider MetadataProvider { get; set; }

        /// <summary>
        /// Gets or sets the <see cref="IUrlHelper"/>.
        /// </summary>
        [FromServices]
        public IUrlHelper Url { get; set; }

        [FromServices]
        public IObjectModelValidator ObjectValidator { get; set; }

        /// <summary>
        /// Gets or sets the <see cref="ClaimsPrincipal"/> for user associated with the executing action.
        /// </summary>
        public ClaimsPrincipal User
        {
            get
            {
                return Context?.User;
            }
        }

        /// <summary>
        /// Gets or sets <see cref="ViewDataDictionary"/> used by <see cref="ViewResult"/> and <see cref="ViewBag"/>.
        /// </summary>
        /// <remarks>
        /// By default, this property is activated when <see cref="IControllerActivator"/> activates controllers.
        /// However, when controllers are directly instantiated in user codes, this property is initialized with
        /// <see cref="EmptyModelMetadataProvider"/>.
        /// </remarks>
        [ViewDataDictionary]
        public ViewDataDictionary ViewData
        {
            get
            {
                if (_viewData == null)
                {
                    // This should run only for the controller unit test scenarios
                    _viewData =
                        new ViewDataDictionary(new EmptyModelMetadataProvider(),
                                                ActionContext?.ModelState ?? new ModelStateDictionary());
                }

                return _viewData;
            }
            set
            {
                if (value == null)
                {
                    throw
                        new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, nameof(ViewData));
                }

                _viewData = value;
            }
        }

        /// <summary>
        /// Gets or sets <see cref="ITempDataDictionary"/> used by <see cref="ViewResult"/>.
        /// </summary>
        [FromServices]
        public ITempDataDictionary TempData { get; set; }

        /// <summary>
        /// Gets the dynamic view bag.
        /// </summary>
        public dynamic ViewBag
        {
            get
            {
                if (_viewBag == null)
                {
                    _viewBag = new DynamicViewData(() => ViewData);
                }

                return _viewBag;
            }
        }

        /// <summary>
        /// Creates a <see cref="ViewResult"/> object that renders a view to the response.
        /// </summary>
        /// <returns>The created <see cref="ViewResult"/> object for the response.</returns>
        [NonAction]
        public virtual ViewResult View()
        {
            return View(viewName: null);
        }

        /// <summary>
        /// Creates a <see cref="ViewResult"/> object by specifying a <paramref name="viewName"/>.
        /// </summary>
        /// <param name="viewName">The name of the view that is rendered to the response.</param>
        /// <returns>The created <see cref="ViewResult"/> object for the response.</returns>
        [NonAction]
        public virtual ViewResult View(string viewName)
        {
            return View(viewName, model: null);
        }

        /// <summary>
        /// Creates a <see cref="ViewResult"/> object by specifying a <paramref name="model"/>
        /// to be rendered by the view.
        /// </summary>
        /// <param name="model">The model that is rendered by the view.</param>
        /// <returns>The created <see cref="ViewResult"/> object for the response.</returns>
        [NonAction]
        public virtual ViewResult View(object model)
        {
            return View(viewName: null, model: model);
        }

        /// <summary>
        /// Creates a <see cref="ViewResult"/> object by specifying a <paramref name="viewName"/>
        /// and the <paramref name="model"/> to be rendered by the view.
        /// </summary>
        /// <param name="viewName">The name of the view that is rendered to the response.</param>
        /// <param name="model">The model that is rendered by the view.</param>
        /// <returns>The created <see cref="ViewResult"/> object for the response.</returns>
        [NonAction]
        public virtual ViewResult View(string viewName, object model)
        {
            // Do not override ViewData.Model unless passed a non-null value.
            if (model != null)
            {
                ViewData.Model = model;
            }

            return new ViewResult()
            {
                ViewName = viewName,
                ViewData = ViewData,
                TempData = TempData
            };
        }

        /// <summary>
        /// Creates a <see cref="PartialViewResult"/> object that renders a partial view to the response.
        /// </summary>
        /// <returns>The created <see cref="PartialViewResult"/> object for the response.</returns>
        [NonAction]
        public virtual PartialViewResult PartialView()
        {
            return PartialView(viewName: null);
        }

        /// <summary>
        /// Creates a <see cref="PartialViewResult"/> object by specifying a <paramref name="viewName"/>.
        /// </summary>
        /// <param name="viewName">The name of the view that is rendered to the response.</param>
        /// <returns>The created <see cref="PartialViewResult"/> object for the response.</returns>
        [NonAction]
        public virtual PartialViewResult PartialView(string viewName)
        {
            return PartialView(viewName, model: null);
        }

        /// <summary>
        /// Creates a <see cref="PartialViewResult"/> object by specifying a <paramref name="model"/>
        /// to be rendered by the partial view.
        /// </summary>
        /// <param name="model">The model that is rendered by the partial view.</param>
        /// <returns>The created <see cref="PartialViewResult"/> object for the response.</returns>
        [NonAction]
        public virtual PartialViewResult PartialView(object model)
        {
            return PartialView(viewName: null, model: model);
        }

        /// <summary>
        /// Creates a <see cref="PartialViewResult"/> object by specifying a <paramref name="viewName"/>
        /// and the <paramref name="model"/> to be rendered by the partial view.
        /// </summary>
        /// <param name="viewName">The name of the partial view that is rendered to the response.</param>
        /// <param name="model">The model that is rendered by the partial view.</param>
        /// <returns>The created <see cref="PartialViewResult"/> object for the response.</returns>
        [NonAction]
        public virtual PartialViewResult PartialView(string viewName, object model)
        {
            // Do not override ViewData.Model unless passed a non-null value.
            if (model != null)
            {
                ViewData.Model = model;
            }

            return new PartialViewResult()
            {
                ViewName = viewName,
                ViewData = ViewData,
                TempData = TempData
            };
        }

        /// <summary>
        /// Creates a <see cref="ContentResult"/> object by specifying a <paramref name="content"/> string.
        /// </summary>
        /// <param name="content">The content to write to the response.</param>
        /// <returns>The created <see cref="ContentResult"/> object for the response.</returns>
        [NonAction]
        public virtual ContentResult Content(string content)
        {
            return Content(content, (MediaTypeHeaderValue)null);
        }

        /// <summary>
        /// Creates a <see cref="ContentResult"/> object by specifying a <paramref name="content"/> string
        /// and a content type.
        /// </summary>
        /// <param name="content">The content to write to the response.</param>
        /// <param name="contentType">The content type (MIME type).</param>
        /// <returns>The created <see cref="ContentResult"/> object for the response.</returns>
        [NonAction]
        public virtual ContentResult Content(string content, string contentType)
        {
            return Content(content, contentType, contentEncoding: null);
        }

        /// <summary>
        /// Creates a <see cref="ContentResult"/> object by specifying a <paramref name="content"/> string,
        /// a <paramref name="contentType"/>, and <paramref name="contentEncoding"/>.
        /// </summary>
        /// <param name="content">The content to write to the response.</param>
        /// <param name="contentType">The content type (MIME type).</param>
        /// <param name="contentEncoding">The content encoding.</param>
        /// <returns>The created <see cref="ContentResult"/> object for the response.</returns>
        [NonAction]
        public virtual ContentResult Content(string content, string contentType, Encoding contentEncoding)
        {
            return Content(content, new MediaTypeHeaderValue(contentType) { Encoding = contentEncoding });
        }

        /// <summary>
        /// Creates a <see cref="ContentResult"/> object by specifying a <paramref name="content"/>
        /// string and a <paramref name="contentType"/>.
        /// </summary>
        /// <param name="content">The content to write to the response.</param>
        /// <param name="contentType">The content type (MIME type).</param>
        /// <returns>The created <see cref="ContentResult"/> object for the response.</returns>
        [NonAction]
        public virtual ContentResult Content(string content, MediaTypeHeaderValue contentType)
        {
            var result = new ContentResult
            {
                Content = content,
                ContentType = contentType
            };

            return result;
        }

        /// <summary>
        /// Creates a <see cref="JsonResult"/> object that serializes the specified <paramref name="data"/> object
        /// to JSON.
        /// </summary>
        /// <param name="data">The object to serialize.</param>
        /// <returns>The created <see cref="JsonResult"/> that serializes the specified <paramref name="data"/>
        /// to JSON format for the response.</returns>
        [NonAction]
        public virtual JsonResult Json(object data)
        {
            var disposableValue = data as IDisposable;
            if (disposableValue != null)
            {
                Response.RegisterForDispose(disposableValue);
            }

            return new JsonResult(data);
        }

        /// <summary>
        /// Creates a <see cref="JsonResult"/> object that serializes the specified <paramref name="data"/> object
        /// to JSON.
        /// </summary>
        /// <param name="data">The object to serialize.</param>
        /// <param name="serializerSettings">The <see cref="JsonSerializerSettings"/> to be used by
        /// the formatter.</param>
        /// <returns>The created <see cref="JsonResult"/> that serializes the specified <paramref name="data"/>
        /// as JSON format for the response.</returns>
        /// <remarks>Callers should cache an instance of <see cref="JsonSerializerSettings"/> to avoid
        /// recreating cached data with each call.</remarks>
        [NonAction]
        public virtual JsonResult Json(object data, [NotNull] JsonSerializerSettings serializerSettings)
        {
            var disposableValue = data as IDisposable;
            if (disposableValue != null)
            {
                Response.RegisterForDispose(disposableValue);
            }

            return new JsonResult(data, serializerSettings);
        }

        /// <summary>
        /// Creates a <see cref="RedirectResult"/> object that redirects to the specified <paramref name="url"/>.
        /// </summary>
        /// <param name="url">The URL to redirect to.</param>
        /// <returns>The created <see cref="RedirectResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectResult Redirect(string url)
        {
            if (string.IsNullOrEmpty(url))
            {
                throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, nameof(url));
            }

            return new RedirectResult(url);
        }

        /// <summary>
        /// Creates a <see cref="RedirectResult"/> object with <see cref="RedirectResult.Permanent"/> set to true
        /// using the specified <paramref name="url"/>.
        /// </summary>
        /// <param name="url">The URL to redirect to.</param>
        /// <returns>The created <see cref="RedirectResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectResult RedirectPermanent(string url)
        {
            if (string.IsNullOrEmpty(url))
            {
                throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, nameof(url));
            }

            return new RedirectResult(url, permanent: true);
        }

        /// <summary>
        /// Redirects to the specified action using the <paramref name="actionName"/>.
        /// </summary>
        /// <param name="actionName">The name of the action.</param>
        /// <returns>The created <see cref="RedirectToActionResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectToActionResult RedirectToAction(string actionName)
        {
            return RedirectToAction(actionName, routeValues: null);
        }

        /// <summary>
        /// Redirects to the specified action using the <paramref name="actionName"/>
        /// and <paramref name="routeValues"/>.
        /// </summary>
        /// <param name="actionName">The name of the action.</param>
        /// <param name="routeValues">The parameters for a route.</param>
        /// <returns>The created <see cref="RedirectToActionResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectToActionResult RedirectToAction(string actionName, object routeValues)
        {
            return RedirectToAction(actionName, controllerName: null, routeValues: routeValues);
        }

        /// <summary>
        /// Redirects to the specified action using the <paramref name="actionName"/>
        /// and the <paramref name="controllerName"/>.
        /// </summary>
        /// <param name="actionName">The name of the action.</param>
        /// <param name="controllerName">The name of the controller.</param>
        /// <returns>The created <see cref="RedirectToActionResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectToActionResult RedirectToAction(string actionName, string controllerName)
        {
            return RedirectToAction(actionName, controllerName, routeValues: null);
        }

        /// <summary>
        /// Redirects to the specified action using the specified <paramref name="actionName"/>,
        /// <paramref name="controllerName"/>, and <paramref name="routeValues"/>.
        /// </summary>
        /// <param name="actionName">The name of the action.</param>
        /// <param name="controllerName">The name of the controller.</param>
        /// <param name="routeValues">The parameters for a route.</param>
        /// <returns>The created <see cref="RedirectToActionResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectToActionResult RedirectToAction(string actionName, string controllerName,
                                        object routeValues)
        {
            return new RedirectToActionResult(actionName, controllerName, PropertyHelper.ObjectToDictionary(routeValues))
            {
                UrlHelper = Url,
            };
        }

        /// <summary>
        /// Redirects to the specified action with <see cref="RedirectToActionResult.Permanent"/> set to true
        /// using the specified <paramref name="actionName"/>.
        /// </summary>
        /// <param name="actionName">The name of the action.</param>
        /// <returns>The created <see cref="RedirectToActionResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectToActionResult RedirectToActionPermanent(string actionName)
        {
            return RedirectToActionPermanent(actionName, routeValues: null);
        }

        /// <summary>
        /// Redirects to the specified action with <see cref="RedirectToActionResult.Permanent"/> set to true
        /// using the specified <paramref name="actionName"/> and <paramref name="routeValues"/>.
        /// </summary>
        /// <param name="actionName">The name of the action.</param>
        /// <param name="routeValues">The parameters for a route.</param>
        /// <returns>The created <see cref="RedirectToActionResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectToActionResult RedirectToActionPermanent(string actionName, object routeValues)
        {
            return RedirectToActionPermanent(actionName, controllerName: null, routeValues: routeValues);
        }

        /// <summary>
        /// Redirects to the specified action with <see cref="RedirectToActionResult.Permanent"/> set to true
        /// using the specified <paramref name="actionName"/> and <paramref name="controllerName"/>.
        /// </summary>
        /// <param name="actionName">The name of the action.</param>
        /// <param name="controllerName">The name of the controller.</param>
        /// <returns>The created <see cref="RedirectToActionResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectToActionResult RedirectToActionPermanent(string actionName, string controllerName)
        {
            return RedirectToActionPermanent(actionName, controllerName, routeValues: null);
        }

        /// <summary>
        /// Redirects to the specified action with <see cref="RedirectToActionResult.Permanent"/> set to true
        /// using the specified <paramref name="actionName"/>, <paramref name="controllerName"/>,
        /// and <paramref name="routeValues"/>.
        /// </summary>
        /// <param name="actionName">The name of the action.</param>
        /// <param name="controllerName">The name of the controller.</param>
        /// <param name="routeValues">The parameters for a route.</param>
        /// <returns>The created <see cref="RedirectToActionResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectToActionResult RedirectToActionPermanent(string actionName, string controllerName,
                                        object routeValues)
        {
            return new RedirectToActionResult(
                actionName,
                controllerName,
                PropertyHelper.ObjectToDictionary(routeValues),
                permanent: true)
            {
                UrlHelper = Url,
            };
        }

        /// <summary>
        /// Redirects to the specified route using the specified <paramref name="routeName"/>.
        /// </summary>
        /// <param name="routeName">The name of the route.</param>
        /// <returns>The created <see cref="RedirectToRouteResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectToRouteResult RedirectToRoute(string routeName)
        {
            return RedirectToRoute(routeName, routeValues: null);
        }

        /// <summary>
        /// Redirects to the specified route using the specified <paramref name="routeValues"/>.
        /// </summary>
        /// <param name="routeValues">The parameters for a route.</param>
        /// <returns>The created <see cref="RedirectToRouteResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectToRouteResult RedirectToRoute(object routeValues)
        {
            return RedirectToRoute(routeName: null, routeValues: routeValues);
        }

        /// <summary>
        /// Redirects to the specified route using the specified <paramref name="routeName"/>
        /// and <paramref name="routeValues"/>.
        /// </summary>
        /// <param name="routeName">The name of the route.</param>
        /// <param name="routeValues">The parameters for a route.</param>
        /// <returns>The created <see cref="RedirectToRouteResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectToRouteResult RedirectToRoute(string routeName, object routeValues)
        {
            return new RedirectToRouteResult(routeName, routeValues)
            {
                UrlHelper = Url,
            };
        }

        /// <summary>
        /// Redirects to the specified route with <see cref="RedirectToRouteResult.Permanent"/> set to true
        /// using the specified <paramref name="routeName"/>.
        /// </summary>
        /// <param name="routeName">The name of the route.</param>
        /// <returns>The created <see cref="RedirectToRouteResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectToRouteResult RedirectToRoutePermanent(string routeName)
        {
            return RedirectToRoutePermanent(routeName, routeValues: null);
        }

        /// <summary>
        /// Redirects to the specified route with <see cref="RedirectToRouteResult.Permanent"/> set to true
        /// using the specified <paramref name="routeValues"/>.
        /// </summary>
        /// <param name="routeValues">The parameters for a route.</param>
        /// <returns>The created <see cref="RedirectToRouteResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectToRouteResult RedirectToRoutePermanent(object routeValues)
        {
            return RedirectToRoutePermanent(routeName: null, routeValues: routeValues);
        }

        /// <summary>
        /// Redirects to the specified route with <see cref="RedirectToRouteResult.Permanent"/> set to true
        /// using the specified <paramref name="routeName"/> and <paramref name="routeValues"/>.
        /// </summary>
        /// <param name="routeName">The name of the route.</param>
        /// <param name="routeValues">The parameters for a route.</param>
        /// <returns>The created <see cref="RedirectToRouteResult"/> for the response.</returns>
        [NonAction]
        public virtual RedirectToRouteResult RedirectToRoutePermanent(string routeName, object routeValues)
        {
            return new RedirectToRouteResult(routeName, routeValues, permanent: true)
            {
                UrlHelper = Url,
            };
        }

        /// <summary>
        /// Returns a file with the specified <paramref name="fileContents" /> as content and the
        /// specified <paramref name="contentType" /> as the Content-Type.
        /// </summary>
        /// <param name="fileContents">The file contents.</param>
        /// <param name="contentType">The Content-Type of the file.</param>
        /// <returns>The created <see cref="FileContentResult"/> for the response.</returns>
        [NonAction]
        public virtual FileContentResult File(byte[] fileContents, string contentType)
        {
            return File(fileContents, contentType, fileDownloadName: null);
        }

        /// <summary>
        /// Returns a file with the specified <paramref name="fileContents" /> as content, the
        /// specified <paramref name="contentType" /> as the Content-Type and the
        /// specified <paramref name="fileDownloadName" /> as the suggested file name.
        /// </summary>
        /// <param name="fileContents">The file contents.</param>
        /// <param name="contentType">The Content-Type of the file.</param>
        /// <param name="fileDownloadName">The suggested file name.</param>
        /// <returns>The created <see cref="FileContentResult"/> for the response.</returns>
        [NonAction]
        public virtual FileContentResult File(byte[] fileContents, string contentType, string fileDownloadName)
        {
            return new FileContentResult(fileContents, contentType) { FileDownloadName = fileDownloadName };
        }

        /// <summary>
        /// Returns a file in the specified <paramref name="fileStream" /> with the
        /// specified <paramref name="contentType" /> as the Content-Type.
        /// </summary>
        /// <param name="fileStream">The <see cref="Stream"/> with the contents of the file.</param>
        /// <param name="contentType">The Content-Type of the file.</param>
        /// <returns>The created <see cref="FileStreamResult"/> for the response.</returns>
        [NonAction]
        public virtual FileStreamResult File(Stream fileStream, string contentType)
        {
            return File(fileStream, contentType, fileDownloadName: null);
        }

        /// <summary>
        /// Returns a file in the specified <paramref name="fileStream" /> with the
        /// specified <paramref name="contentType" /> as the Content-Type and the
        /// specified <paramref name="fileDownloadName" /> as the suggested file name.
        /// </summary>
        /// <param name="fileStream">The <see cref="Stream"/> with the contents of the file.</param>
        /// <param name="contentType">The Content-Type of the file.</param>
        /// <param name="fileDownloadName">The suggested file name.</param>
        /// <returns>The created <see cref="FileStreamResult"/> for the response.</returns>
        [NonAction]
        public virtual FileStreamResult File(Stream fileStream, string contentType, string fileDownloadName)
        {
            if (fileStream != null)
            {
                Response.RegisterForDispose(fileStream);
            }

            return new FileStreamResult(fileStream, contentType) { FileDownloadName = fileDownloadName };
        }

        /// <summary>
        /// Returns the file specified by <paramref name="fileName" /> with the
        /// specified <paramref name="contentType" /> as the Content-Type.
        /// </summary>
        /// <param name="fileName">The <see cref="Stream"/> with the contents of the file.</param>
        /// <param name="contentType">The Content-Type of the file.</param>
        /// <returns>The created <see cref="FilePathResult"/> for the response.</returns>
        [NonAction]
        public virtual FilePathResult File(string fileName, string contentType)
        {
            return File(fileName, contentType, fileDownloadName: null);
        }

        /// <summary>
        /// Returns the file specified by <paramref name="fileName" /> with the
        /// specified <paramref name="contentType" /> as the Content-Type and the
        /// specified <paramref name="fileDownloadName" /> as the suggested file name.
        /// </summary>
        /// <param name="fileName">The <see cref="Stream"/> with the contents of the file.</param>
        /// <param name="contentType">The Content-Type of the file.</param>
        /// <param name="fileDownloadName">The suggested file name.</param>
        /// <returns>The created <see cref="FilePathResult"/> for the response.</returns>
        [NonAction]
        public virtual FilePathResult File(string fileName, string contentType, string fileDownloadName)
        {
            return new FilePathResult(fileName, contentType) { FileDownloadName = fileDownloadName };
        }

        /// <summary>
        /// Creates an <see cref="HttpUnauthorizedResult"/> that produces an Unauthorized (401) response.
        /// </summary>
        /// <returns>The created <see cref="HttpUnauthorizedResult"/> for the response.</returns>
        [NonAction]
        public virtual HttpUnauthorizedResult HttpUnauthorized()
        {
            return new HttpUnauthorizedResult();
        }

        /// <summary>
        /// Creates an <see cref="HttpNotFoundResult"/> that produces a Not Found (404) response.
        /// </summary>
        /// <returns>The created <see cref="HttpNotFoundResult"/> for the response.</returns>
        [NonAction]
        public virtual HttpNotFoundResult HttpNotFound()
        {
            return new HttpNotFoundResult();
        }

        /// <summary>
        /// Creates an <see cref="HttpNotFoundObjectResult"/> that produces a Not Found (404) response.
        /// </summary>
        /// <returns>The created <see cref="HttpNotFoundObjectResult"/> for the response.</returns>
        [NonAction]
        public virtual HttpNotFoundObjectResult HttpNotFound(object value)
        {
            var disposableValue = value as IDisposable;
            if (disposableValue != null)
            {
                Response.RegisterForDispose(disposableValue);
            }

            return new HttpNotFoundObjectResult(value);
        }

        /// <summary>
        /// Creates an <see cref="BadRequestResult"/> that produces a Bad Request (400) response.
        /// </summary>
        /// <returns>The created <see cref="BadRequestResult"/> for the response.</returns>
        [NonAction]
        public virtual BadRequestResult HttpBadRequest()
        {
            return new BadRequestResult();
        }

        /// <summary>
        /// Creates an <see cref="BadRequestObjectResult"/> that produces a Bad Request (400) response.
        /// </summary>
        /// <returns>The created <see cref="BadRequestObjectResult"/> for the response.</returns>
        [NonAction]
        public virtual BadRequestObjectResult HttpBadRequest(object error)
        {
            var disposableValue = error as IDisposable;
            if (disposableValue != null)
            {
                Response.RegisterForDispose(disposableValue);
            }

            return new BadRequestObjectResult(error);
        }

        /// <summary>
        /// Creates an <see cref="BadRequestObjectResult"/> that produces a Bad Request (400) response.
        /// </summary>
        /// <returns>The created <see cref="BadRequestObjectResult"/> for the response.</returns>
        [NonAction]
        public virtual BadRequestObjectResult HttpBadRequest([NotNull] ModelStateDictionary modelState)
        {
            return new BadRequestObjectResult(modelState);
        }

        /// <summary>
        /// Creates a <see cref="CreatedResult"/> object that produces a Created (201) response.
        /// </summary>
        /// <param name="uri">The URI at which the content has been created.</param>
        /// <param name="value">The content value to format in the entity body.</param>
        /// <returns>The created <see cref="CreatedResult"/> for the response.</returns>
        [NonAction]
        public virtual CreatedResult Created([NotNull] string uri, object value)
        {
            var disposableValue = value as IDisposable;
            if (disposableValue != null)
            {
                Response.RegisterForDispose(disposableValue);
            }

            return new CreatedResult(uri, value);
        }

        /// <summary>
        /// Creates a <see cref="CreatedResult"/> object that produces a Created (201) response.
        /// </summary>
        /// <param name="uri">The URI at which the content has been created.</param>
        /// <param name="value">The content value to format in the entity body.</param>
        /// <returns>The created <see cref="CreatedResult"/> for the response.</returns>
        [NonAction]
        public virtual CreatedResult Created([NotNull] Uri uri, object value)
        {
            string location;
            if (uri.IsAbsoluteUri)
            {
                location = uri.AbsoluteUri;
            }
            else
            {
                location = uri.GetComponents(UriComponents.SerializationInfoString, UriFormat.UriEscaped);
            }

            return Created(location, value);
        }

        /// <summary>
        /// Creates a <see cref="CreatedAtActionResult"/> object that produces a Created (201) response.
        /// </summary>
        /// <param name="actionName">The name of the action to use for generating the URL.</param>
        /// <param name="value">The content value to format in the entity body.</param>
        /// <returns>The created <see cref="CreatedAtRouteResult"/> for the response.</returns>
        [NonAction]
        public virtual CreatedAtActionResult CreatedAtAction(string actionName, object value)
        {
            return CreatedAtAction(actionName, routeValues: null, value: value);
        }

        /// <summary>
        /// Creates a <see cref="CreatedAtActionResult"/> object that produces a Created (201) response.
        /// </summary>
        /// <param name="actionName">The name of the action to use for generating the URL.</param>
        /// <param name="routeValues">The route data to use for generating the URL.</param>
        /// <param name="value">The content value to format in the entity body.</param>
        /// <returns>The created <see cref="CreatedAtRouteResult"/> for the response.</returns>
        [NonAction]
        public virtual CreatedAtActionResult CreatedAtAction(string actionName, object routeValues, object value)
        {
            return CreatedAtAction(actionName, controllerName: null, routeValues: routeValues, value: value);
        }

        /// <summary>
        /// Creates a <see cref="CreatedAtActionResult"/> object that produces a Created (201) response.
        /// </summary>
        /// <param name="actionName">The name of the action to use for generating the URL.</param>
        /// <param name="controllerName">The name of the controller to use for generating the URL.</param>
        /// <param name="routeValues">The route data to use for generating the URL.</param>
        /// <param name="value">The content value to format in the entity body.</param>
        /// <returns>The created <see cref="CreatedAtRouteResult"/> for the response.</returns>
        [NonAction]
        public virtual CreatedAtActionResult CreatedAtAction(string actionName,
                                                             string controllerName,
                                                             object routeValues,
                                                             object value)
        {
            var disposableValue = value as IDisposable;
            if (disposableValue != null)
            {
                Response.RegisterForDispose(disposableValue);
            }

            return new CreatedAtActionResult(actionName, controllerName, routeValues, value);
        }

        /// <summary>
        /// Creates a <see cref="CreatedAtRouteResult"/> object that produces a Created (201) response.
        /// </summary>
        /// <param name="routeName">The name of the route to use for generating the URL.</param>
        /// <param name="value">The content value to format in the entity body.</param>
        /// <returns>The created <see cref="CreatedAtRouteResult"/> for the response.</returns>
        [NonAction]
        public virtual CreatedAtRouteResult CreatedAtRoute(string routeName, object value)
        {
            return CreatedAtRoute(routeName, routeValues: null, value: value);
        }

        /// <summary>
        /// Creates a <see cref="CreatedAtRouteResult"/> object that produces a Created (201) response.
        /// </summary>
        /// <param name="routeValues">The route data to use for generating the URL.</param>
        /// <param name="value">The content value to format in the entity body.</param>
        /// <returns>The created <see cref="CreatedAtRouteResult"/> for the response.</returns>
        [NonAction]
        public virtual CreatedAtRouteResult CreatedAtRoute(object routeValues, object value)
        {
            return CreatedAtRoute(routeName: null, routeValues: routeValues, value: value);
        }

        /// <summary>
        /// Creates a <see cref="CreatedAtRouteResult"/> object that produces a Created (201) response.
        /// </summary>
        /// <param name="routeName">The name of the route to use for generating the URL.</param>
        /// <param name="routeValues">The route data to use for generating the URL.</param>
        /// <param name="value">The content value to format in the entity body.</param>
        /// <returns>The created <see cref="CreatedAtRouteResult"/> for the response.</returns>
        [NonAction]
        public virtual CreatedAtRouteResult CreatedAtRoute(string routeName, object routeValues, object value)
        {
            var disposableValue = value as IDisposable;
            if (disposableValue != null)
            {
                Response.RegisterForDispose(disposableValue);
            }

            return new CreatedAtRouteResult(routeName, routeValues, value);
        }

        /// <summary>
        /// Called before the action method is invoked.
        /// </summary>
        /// <param name="context">The action executing context.</param>
        [NonAction]
        public virtual void OnActionExecuting([NotNull] ActionExecutingContext context)
        {
        }

        /// <summary>
        /// Called after the action method is invoked.
        /// </summary>
        /// <param name="context">The action executed context.</param>
        [NonAction]
        public virtual void OnActionExecuted([NotNull] ActionExecutedContext context)
        {
        }

        /// <summary>
        /// Called before the action method is invoked.
        /// </summary>
        /// <param name="context">The action executing context.</param>
        /// <param name="next">The <see cref="ActionExecutionDelegate"/> to execute. Invoke this delegate in the body
        /// of <see cref="OnActionExecutionAsync" /> to continue execution of the action.</param>
        /// <returns>A <see cref="Task"/> instance.</returns>
        [NonAction]
        public virtual async Task OnActionExecutionAsync(
            [NotNull] ActionExecutingContext context,
            [NotNull] ActionExecutionDelegate next)
        {
            OnActionExecuting(context);
            if (context.Result == null)
            {
                OnActionExecuted(await next());
            }
        }

        /// <summary>
        /// Updates the specified <paramref name="model"/> instance using values from the controller's current
        /// <see cref="IValueProvider"/>.
        /// </summary>
        /// <typeparam name="TModel">The type of the model object.</typeparam>
        /// <param name="model">The model instance to update.</param>
        /// <returns>A <see cref="Task"/> that on completion returns <c>true</c> if the update is successful</returns>
        [NonAction]
        public virtual Task<bool> TryUpdateModelAsync<TModel>([NotNull] TModel model)
            where TModel : class
        {
            return TryUpdateModelAsync(model, prefix: string.Empty);
        }

        /// <summary>
        /// Updates the specified <paramref name="model"/> instance using values from the controller's current
        /// <see cref="IValueProvider"/> and a <paramref name="prefix"/>.
        /// </summary>
        /// <typeparam name="TModel">The type of the model object.</typeparam>
        /// <param name="model">The model instance to update.</param>
        /// <param name="prefix">The prefix to use when looking up values in the current <see cref="IValueProvider"/>
        /// </param>
        /// <returns>A <see cref="Task"/> that on completion returns <c>true</c> if the update is successful</returns>
        [NonAction]
        public virtual async Task<bool> TryUpdateModelAsync<TModel>([NotNull] TModel model,
                                                                    [NotNull] string prefix)
            where TModel : class
        {
            if (BindingContext == null)
            {
                var message = Resources.FormatPropertyOfTypeCannotBeNull(
                    nameof(BindingContext),
                    typeof(Controller).FullName);
                throw new InvalidOperationException(message);
            }

            return await TryUpdateModelAsync(model, prefix, BindingContext.ValueProvider);
        }

        /// <summary>
        /// Updates the specified <paramref name="model"/> instance using the <paramref name="valueProvider"/> and a
        /// <paramref name="prefix"/>.
        /// </summary>
        /// <typeparam name="TModel">The type of the model object.</typeparam>
        /// <param name="model">The model instance to update.</param>
        /// <param name="prefix">The prefix to use when looking up values in the <paramref name="valueProvider"/>.
        /// </param>
        /// <param name="valueProvider">The <see cref="IValueProvider"/> used for looking up values.</param>
        /// <returns>A <see cref="Task"/> that on completion returns <c>true</c> if the update is successful</returns>
        [NonAction]
        public virtual async Task<bool> TryUpdateModelAsync<TModel>([NotNull] TModel model,
                                                                    [NotNull] string prefix,
                                                                    [NotNull] IValueProvider valueProvider)
            where TModel : class
        {
            if (BindingContext == null)
            {
                var message = Resources.FormatPropertyOfTypeCannotBeNull(
                    nameof(BindingContext),
                    typeof(Controller).FullName);
                throw new InvalidOperationException(message);
            }

            return await ModelBindingHelper.TryUpdateModelAsync(
                model,
                prefix,
                ActionContext.HttpContext,
                ModelState,
                MetadataProvider,
                BindingContext.ModelBinder,
                valueProvider,
                BindingContext.InputFormatters,
                ObjectValidator,
                BindingContext.ValidatorProvider);
        }

        /// <summary>
        /// Updates the specified <paramref name="model"/> instance using values from the controller's current
        /// <see cref="IValueProvider"/> and a <paramref name="prefix"/>.
        /// </summary>
        /// <typeparam name="TModel">The type of the model object.</typeparam>
        /// <param name="model">The model instance to update.</param>
        /// <param name="prefix">The prefix to use when looking up values in the current <see cref="IValueProvider"/>.
        /// </param>
        /// <param name="includeExpressions"> <see cref="Expression"/>(s) which represent top-level properties
        /// which need to be included for the current model.</param>
        /// <returns>A <see cref="Task"/> that on completion returns <c>true</c> if the update is successful</returns>
        [NonAction]
        public async Task<bool> TryUpdateModelAsync<TModel>(
            [NotNull] TModel model,
            string prefix,
            [NotNull] params Expression<Func<TModel, object>>[] includeExpressions)
           where TModel : class
        {
            if (BindingContext == null)
            {
                var message = Resources.FormatPropertyOfTypeCannotBeNull(
                    nameof(BindingContext),
                    typeof(Controller).FullName);
                throw new InvalidOperationException(message);
            }

            return await ModelBindingHelper.TryUpdateModelAsync(
                model,
                prefix,
                ActionContext.HttpContext,
                ModelState,
                MetadataProvider,
                BindingContext.ModelBinder,
                BindingContext.ValueProvider,
                BindingContext.InputFormatters,
                ObjectValidator,
                BindingContext.ValidatorProvider,
                includeExpressions);
        }

        /// <summary>
        /// Updates the specified <paramref name="model"/> instance using values from the controller's current
        /// <see cref="IValueProvider"/> and a <paramref name="prefix"/>.
        /// </summary>
        /// <typeparam name="TModel">The type of the model object.</typeparam>
        /// <param name="model">The model instance to update.</param>
        /// <param name="prefix">The prefix to use when looking up values in the current <see cref="IValueProvider"/>.
        /// </param>
        /// <param name="predicate">A predicate which can be used to filter properties at runtime.</param>
        /// <returns>A <see cref="Task"/> that on completion returns <c>true</c> if the update is successful</returns>
        [NonAction]
        public async Task<bool> TryUpdateModelAsync<TModel>(
            [NotNull] TModel model,
            string prefix,
            [NotNull] Func<ModelBindingContext, string, bool> predicate)
            where TModel : class
        {
            if (BindingContext == null)
            {
                var message = Resources.FormatPropertyOfTypeCannotBeNull(
                    nameof(BindingContext),
                    typeof(Controller).FullName);
                throw new InvalidOperationException(message);
            }

            return await ModelBindingHelper.TryUpdateModelAsync(
                model,
                prefix,
                ActionContext.HttpContext,
                ModelState,
                MetadataProvider,
                BindingContext.ModelBinder,
                BindingContext.ValueProvider,
                BindingContext.InputFormatters,
                ObjectValidator,
                BindingContext.ValidatorProvider,
                predicate);
        }

        /// <summary>
        /// Updates the specified <paramref name="model"/> instance using the <paramref name="valueProvider"/> and a
        /// <paramref name="prefix"/>.
        /// </summary>
        /// <typeparam name="TModel">The type of the model object.</typeparam>
        /// <param name="model">The model instance to update.</param>
        /// <param name="prefix">The prefix to use when looking up values in the <paramref name="valueProvider"/>
        /// </param>
        /// <param name="valueProvider">The <see cref="IValueProvider"/> used for looking up values.</param>
        /// <param name="includeExpressions"> <see cref="Expression"/>(s) which represent top-level properties
        /// which need to be included for the current model.</param>
        /// <returns>A <see cref="Task"/> that on completion returns <c>true</c> if the update is successful</returns>
        [NonAction]
        public async Task<bool> TryUpdateModelAsync<TModel>(
            [NotNull] TModel model,
            string prefix,
            [NotNull] IValueProvider valueProvider,
            [NotNull] params Expression<Func<TModel, object>>[] includeExpressions)
           where TModel : class
        {
            if (BindingContext == null)
            {
                var message = Resources.FormatPropertyOfTypeCannotBeNull(
                    nameof(BindingContext),
                    typeof(Controller).FullName);
                throw new InvalidOperationException(message);
            }

            return await ModelBindingHelper.TryUpdateModelAsync(
                model,
                prefix,
                ActionContext.HttpContext,
                ModelState,
                MetadataProvider,
                BindingContext.ModelBinder,
                valueProvider,
                BindingContext.InputFormatters,
                ObjectValidator,
                BindingContext.ValidatorProvider,
                includeExpressions);
        }

        /// <summary>
        /// Updates the specified <paramref name="model"/> instance using the <paramref name="valueProvider"/> and a
        /// <paramref name="prefix"/>.
        /// </summary>
        /// <typeparam name="TModel">The type of the model object.</typeparam>
        /// <param name="model">The model instance to update.</param>
        /// <param name="prefix">The prefix to use when looking up values in the <paramref name="valueProvider"/>
        /// </param>
        /// <param name="valueProvider">The <see cref="IValueProvider"/> used for looking up values.</param>
        /// <param name="predicate">A predicate which can be used to filter properties at runtime.</param>
        /// <returns>A <see cref="Task"/> that on completion returns <c>true</c> if the update is successful</returns>
        [NonAction]
        public async Task<bool> TryUpdateModelAsync<TModel>(
            [NotNull] TModel model,
            string prefix,
            [NotNull] IValueProvider valueProvider,
            [NotNull] Func<ModelBindingContext, string, bool> predicate)
            where TModel : class
        {
            if (BindingContext == null)
            {
                var message = Resources.FormatPropertyOfTypeCannotBeNull(
                    nameof(BindingContext),
                    typeof(Controller).FullName);
                throw new InvalidOperationException(message);
            }

            return await ModelBindingHelper.TryUpdateModelAsync(
                model,
                prefix,
                ActionContext.HttpContext,
                ModelState,
                MetadataProvider,
                BindingContext.ModelBinder,
                valueProvider,
                BindingContext.InputFormatters,
                ObjectValidator,
                BindingContext.ValidatorProvider,
                predicate);
        }

        /// <summary>
        /// Updates the specified <paramref name="model"/> instance using values from the controller's current
        /// <see cref="IValueProvider"/> and a <paramref name="prefix"/>.
        /// </summary>
        /// <param name="model">The model instance to update.</param>
        /// <param name="modelType">The type of model instance to update.</param>
        /// <param name="prefix">The prefix to use when looking up values in the current <see cref="IValueProvider"/>
        /// </param>
        /// <returns>A <see cref="Task"/> that on completion returns <c>true</c> if the update is successful</returns>
        [NonAction]
        public virtual async Task<bool> TryUpdateModelAsync([NotNull] object model,
                                                            [NotNull] Type modelType,
                                                            string prefix)
        {
            if (BindingContext == null)
            {
                var message = Resources.FormatPropertyOfTypeCannotBeNull(
                    nameof(BindingContext),
                    typeof(Controller).FullName);
                throw new InvalidOperationException(message);
            }

            return await ModelBindingHelper.TryUpdateModelAsync(
                model,
                modelType,
                prefix,
                ActionContext.HttpContext,
                ModelState,
                MetadataProvider,
                BindingContext.ModelBinder,
                BindingContext.ValueProvider,
                BindingContext.InputFormatters,
                ObjectValidator,
                BindingContext.ValidatorProvider);
        }

        /// <summary>
        /// Updates the specified <paramref name="model"/> instance using the <paramref name="valueProvider"/> and a
        /// <paramref name="prefix"/>.
        /// </summary>
        /// <param name="model">The model instance to update.</param>
        /// <param name="modelType">The type of model instance to update.</param>
        /// <param name="prefix">The prefix to use when looking up values in the <paramref name="valueProvider"/>
        /// </param>
        /// <param name="valueProvider">The <see cref="IValueProvider"/> used for looking up values.</param>
        /// <param name="predicate">A predicate which can be used to filter properties at runtime.</param>
        /// <returns>A <see cref="Task"/> that on completion returns <c>true</c> if the update is successful</returns>
        [NonAction]
        public async Task<bool> TryUpdateModelAsync(
            [NotNull] object model,
            [NotNull] Type modelType,
            string prefix,
            [NotNull] IValueProvider valueProvider,
            [NotNull] Func<ModelBindingContext, string, bool> predicate)
        {
            if (BindingContext == null)
            {
                var message = Resources.FormatPropertyOfTypeCannotBeNull(
                    nameof(BindingContext),
                    typeof(Controller).FullName);
                throw new InvalidOperationException(message);
            }

            return await ModelBindingHelper.TryUpdateModelAsync(
                model,
                modelType,
                prefix,
                ActionContext.HttpContext,
                ModelState,
                MetadataProvider,
                BindingContext.ModelBinder,
                valueProvider,
                BindingContext.InputFormatters,
                ObjectValidator,
                BindingContext.ValidatorProvider,
                predicate);
        }

        /// <summary>
        /// Validates the specified <paramref name="model"/> instance.
        /// </summary>
        /// <param name="model">The model to validate.</param>
        /// <returns><c>true</c> if the <see cref="ModelState"/> is valid; <c>false</c> otherwise. </returns>
        [NonAction]
        public virtual bool TryValidateModel([NotNull] object model)
        {
            return TryValidateModel(model, prefix: null);
        }

        /// <summary>
        /// Validates the specified <paramref name="model"/> instance.
        /// </summary>
        /// <param name="model">The model to validate.</param>
        /// <param name="prefix">The key to use when looking up information in <see cref="ModelState"/>.
        /// </param>
        /// <returns><c>true</c> if the <see cref="ModelState"/> is valid;<c>false</c> otherwise. </returns>
        [NonAction]
        public virtual bool TryValidateModel([NotNull] object model, string prefix)
        {
            if (BindingContext == null)
            {
                var message = Resources.FormatPropertyOfTypeCannotBeNull(
                    nameof(BindingContext),
                    typeof(Controller).FullName);
                throw new InvalidOperationException(message);
            }

            var modelExplorer = MetadataProvider.GetModelExplorerForType(model.GetType(), model);

            var modelName = prefix ?? string.Empty;

            // Clear ModelStateDictionary entries for the model so that it will be re-validated.
            ModelBindingHelper.ClearValidationStateForModel(
                model.GetType(),
                ModelState,
                MetadataProvider,
                modelName);

            var validationContext = new ModelValidationContext(
                bindingSource: null,
                validatorProvider: BindingContext.ValidatorProvider,
                modelState: ModelState,
                modelExplorer: modelExplorer);

            ObjectValidator.Validate(
                validationContext,
                new ModelValidationNode(modelName, modelExplorer.Metadata, model)
                {
                    ValidateAllProperties = true
                });
            return ModelState.IsValid;
        }

        /// <inheritdoc />
        public void Dispose()
        {
            Dispose(disposing: true);
            GC.SuppressFinalize(this);
        }

        /// <summary>
        /// Releases all resources currently used by this <see cref="Controller"/> instance.
        /// </summary>
        /// <param name="disposing"><c>true</c> if this method is being invoked by the <see cref="Dispose"/> method,
        /// otherwise <c>false</c>.</param>
        protected virtual void Dispose(bool disposing)
        {
        }
    }
}