如何确保控制器和动作存在之前做重定向，asp.net mvc3

Question

在我的一个控制器+动作对中，我从某个地方获得另一个控制器和动作的值作为字符串，我想重定向我的当前动作。在进行重定向之前，我要确保controller+action存在于我的应用程序中，如果不存在则重定向到404。我正在寻找一种方法来做到这一点。

public ActionResult MyTestAction()
{
    string controller = getFromSomewhere();
    string action = getFromSomewhereToo();
    /*
      At this point use reflection and make sure action and controller exists
      else redirect to error 404
    */ 
    return RedirectToRoute(new { action = action, controller = controller });
}

我所做的就是这些，但是它不工作。

var cont = Assembly.GetExecutingAssembly().GetType(controller);
if (cont != null && cont.GetMethod(action) != null)
{ 
    // controller and action pair is valid
}
else
{ 
    // controller and action pair is invalid
}

Answer 1

你可以实现IRouteConstraint并在你的路由表中使用它。

这个路由约束的实现可以使用反射来检查controller/action是否存在。如果不存在，则跳过该路由。作为路由表中的最后一个路由，你可以设置一个捕获所有路由，并将其映射到呈现404视图的操作。

这里有一些代码片段来帮助你开始:

public class MyRouteConstraint : IRouteConstraint
    {
        public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values, RouteDirection routeDirection)
        {
            var action = values["action"] as string;
            var controller = values["controller"] as string;
            var controllerFullName = string.Format("MvcApplication1.Controllers.{0}Controller", controller);
            var cont = Assembly.GetExecutingAssembly().GetType(controllerFullName);
            return cont != null && cont.GetMethod(action) != null;
        }
    }

请注意，您需要使用控制器的全限定名称。

RouteConfig.cs

routes.MapRoute(
                "Home", // Route name
                "{controller}/{action}", // URL with parameters
                new { controller = "Home", action = "Index" }, // Parameter defaults
                new { action = new MyRouteConstraint() } //Route constraints
            );
routes.MapRoute(
                "PageNotFound", // Route name
                "{*catchall}", // URL with parameters
                new { controller = "Home", action = "PageNotFound" } // Parameter defaults
            );

Answer 2

如果您无法获得要传递给GetType()的控制器的完全限定名称，则需要使用GetTypes()，然后对结果进行字符串比较。

Type[] types = System.Reflection.Assembly.GetExecutingAssembly().GetTypes();
Type type = types.Where( t => t.Name == controller ).SingleOrDefault();
if( type != null && type.GetMethod( action ) != null )

Answer 3

我们通过在WebApiConfig.cs文件中添加这一行来解决这个问题

config.Services.Replace(typeof(IHttpControllerSelector), new AcceptHeaderControllerSelector(config));

我使用的核心方法如下:这个方法在扩展IHttpControllerSelector接口的AcceptHeaderControllerSelector类中。

我这样做的原因是我们必须对API进行版本化，这是一种创建新控制器的方法，例如V2，我们只使用版本化的方法，如果V2不存在，就回退到V1

private HttpControllerDescriptor TryGetControllerWithMatchingMethod(string version, string controllerName, string actionName)
{
    var versionNumber = Convert.ToInt32(version.Substring(1, version.Length - 1));
    while(versionNumber >= 1) { 
        var controllerFullName = string.Format("Namespace.Controller.V{0}.{1}Controller, Namespace.Controller.V{0}", versionNumber, controllerName);
        Type type = Type.GetType(controllerFullName, false, true);
        var matchFound = type != null && type.GetMethod(actionName) != null;
        if (matchFound)
        {
            var key = string.Format(CultureInfo.InvariantCulture, "V{0}{1}", versionNumber, controllerName);
            HttpControllerDescriptor controllerDescriptor;
            if (_controllers.TryGetValue(key, out controllerDescriptor))
            {
                return controllerDescriptor;
            }
        }
        versionNumber--;
    }
    return null;
}

完整文件如下:

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Reflection;
using System.Web.Http;
using System.Web.Http.Controllers;
using System.Web.Http.Dispatcher;
using System.Web.Http.Routing;
namespace WebApi
{
    public class AcceptHeaderControllerSelector : IHttpControllerSelector
    {
        private const string ControllerKey = "controller";
        private const string ActionKey = "action";
        private const string VersionHeaderValueNotFoundExceptionMessage = "Version not found in headers";
        private const string VersionFoundInUrlAndHeaderErrorMessage = "Version can not be in Header and Url";
        private const string CouldNotFindEndPoint = "Could not find endpoint {0} for api version number {1}";
        private readonly HttpConfiguration _configuration;
        private readonly Dictionary<string, HttpControllerDescriptor> _controllers;
        public AcceptHeaderControllerSelector(HttpConfiguration config)
        {
            _configuration = config;
            _controllers = InitializeControllerDictionary();
        }
        private Dictionary<string, HttpControllerDescriptor> InitializeControllerDictionary()
        {
            var dictionary = new Dictionary<string, HttpControllerDescriptor>(StringComparer.OrdinalIgnoreCase);
            var assembliesResolver = _configuration.Services.GetAssembliesResolver();
            // This would seem to look at all references in the web api project and find any controller, so I had to add Controller.V2 reference in order for it to find them
            var controllersResolver = _configuration.Services.GetHttpControllerTypeResolver();
            var controllerTypes = controllersResolver.GetControllerTypes(assembliesResolver);
            foreach (var t in controllerTypes)
            {
                var segments = t.Namespace.Split(Type.Delimiter);
                // For the dictionary key, strip "Controller" from the end of the type name.
                // This matches the behavior of DefaultHttpControllerSelector.
                var controllerName = t.Name.Remove(t.Name.Length - DefaultHttpControllerSelector.ControllerSuffix.Length);
                var key = string.Format(CultureInfo.InvariantCulture, "{0}{1}", segments[segments.Length - 1], controllerName);
                dictionary[key] = new HttpControllerDescriptor(_configuration, t.Name, t);
            }
            return dictionary;
        }
        public HttpControllerDescriptor SelectController(HttpRequestMessage request)
        {
            IHttpRouteData routeData = request.GetRouteData();
            if (routeData == null)  
            {
                throw new HttpResponseException(HttpStatusCode.NotFound);
            }
            var controllerName = GetRouteVariable<string>(routeData, ControllerKey);
            var actionName = GetRouteVariable<string>(routeData, ActionKey);
            if (controllerName == null)
            {
                throw new HttpResponseException(HttpStatusCode.NotFound);
            }
            var version = GetVersion(request);
            HttpControllerDescriptor controllerDescriptor;
            if (_controllers.TryGetValue(controllerName, out controllerDescriptor))
            {
                if (!string.IsNullOrWhiteSpace(version))
                {
                    throw new HttpResponseException(request.CreateResponse(HttpStatusCode.Forbidden, VersionFoundInUrlAndHeaderErrorMessage));
                }
                return controllerDescriptor;
            }
            controllerDescriptor = TryGetControllerWithMatchingMethod(version, controllerName, actionName);
            if (controllerDescriptor != null)
            {
                return controllerDescriptor;
            }
            var message = string.Format(CouldNotFindEndPoint, controllerName, version);
            throw new HttpResponseException(request.CreateResponse(HttpStatusCode.NotFound, message));
        }
        private HttpControllerDescriptor TryGetControllerWithMatchingMethod(string version, string controllerName, string actionName)
        {
            var versionNumber = Convert.ToInt32(version.Substring(1, version.Length - 1));
            while(versionNumber >= 1) { 
                var controllerFullName = string.Format("Namespace.Controller.V{0}.{1}Controller, Namespace.Controller.V{0}", versionNumber, controllerName);
                Type type = Type.GetType(controllerFullName, false, true);
                var matchFound = type != null && type.GetMethod(actionName) != null;
                if (matchFound)
                {
                    var key = string.Format(CultureInfo.InvariantCulture, "V{0}{1}", versionNumber, controllerName);
                    HttpControllerDescriptor controllerDescriptor;
                    if (_controllers.TryGetValue(key, out controllerDescriptor))
                    {
                        return controllerDescriptor;
                    }
                }
                versionNumber--;
            }
            return null;
        }
        public IDictionary<string, HttpControllerDescriptor> GetControllerMapping()
        {
            return _controllers;
        }
        private string GetVersion(HttpRequestMessage request)
        {
            IEnumerable<string> values;
            string apiVersion = null;
            if (request.Headers.TryGetValues(Common.Classes.Constants.ApiVersion, out values))
            {
                apiVersion = values.FirstOrDefault();
            }
            return apiVersion;
        }
        private static T GetRouteVariable<T>(IHttpRouteData routeData, string name)
        {
            object result = null;
            if (routeData.Values.TryGetValue(name, out result))
            {
                return (T)result;
            }
            return default(T);
        }
    }
}

Answer 4

反射是一个开销很大的操作。

你真的应该对这些方法进行单元测试，以确保它们被重定向到适当的操作和控制器。

。(NUnit)

[Test]
public void MyTestAction_Redirects_To_MyOtherAction()
{
  var controller = new MyController();
  var result = (RedirectToRouteResult)controller.MyTestAction();
  Assert.That(result.RouteValues["action"], Is.EqualTo("MyOtherAction");
  Assert.That(result.RouteValues["controller"], Is.EqualTo("MyOtherController");
}