为什么 ASP.NET MVC 返回与 controller 匹配的多种类型？

Question

我正在尝试使用 ASP.NET MVC4 设置版本化的 API。 Global.asax.cs使用System.Web.Http.GlobalConfiguration.Configuration在我的项目WebApiConfig.Register中调用一个方法。 WebApiConfig.Register的代码如下所示：

public static void Register(HttpConfiguration config)
{
    CreateRoute(
        routes: config.Routes,
        name: "Root",
        routeTemplate: "api",
        defaults: new { },
        constraints: new { },
        namespaces: new[] { "MyApp.Controllers.Api" },
    );

    CreateRoute(
        routes: config.Routes,
        name: "API",
        routeTemplate: "api/{controller}/{action}",
        defaults: new { action = "Get" },
        constraints: new { },
        namespaces: new[] { "MyApp.Controllers.Api" },
    );

    CreateRoute(
        routes: config.Routes,
        name: "API v2",
        routeTemplate: "api/v2/{controller}/{action}",
        defaults: new { action = "Get" },
        constraints: new { },
        namespaces: new[] { "MyApp.Controllers.Api.v2" },
    );
}

private static void CreateRoute(HttpRouteCollection routes, string name, string routeTemplate, object defaults, object constraints, string[] namespaces)
{
    var defaultsDictionary = new HttpRouteValueDictionary(defaults);
    var constraintsDictionary = new HttpRouteValueDictionary(constraints);
    var dataTokensDictionary = new HttpRouteValueDictionary(new { Namespaces = namespaces, UseNamespaceFallback = false });
    var route = routes.CreateRoute(routeTemplate, defaultsDictionary, constraintsDictionary, dataTokensDictionary);
    routes.Add(name, route);
}

我有两个名为UsersController的控制器，一个位于MyApp.Controllers.Api.UsersController ，一个位于MyApp.Controllers.Api.v2.UsersController 。 当我发出POST /api/users/Login之类的请求时，我得到响应500 Multiple types were found that match the controller names 'users'. This can happen if the route that services this request ('api/{controller}/{action}') found multiple controllers defined with the same name but differing namespaces, which is not supported.\r\n\r\nThe request for 'users' has found the following matching controllers:\r\nMyApp.Controllers.Api.v2.UsersController\r\nMyApp.Controllers.Api.UsersController 500 Multiple types were found that match the controller names 'users'. This can happen if the route that services this request ('api/{controller}/{action}') found multiple controllers defined with the same name but differing namespaces, which is not supported.\r\n\r\nThe request for 'users' has found the following matching controllers:\r\nMyApp.Controllers.Api.v2.UsersController\r\nMyApp.Controllers.Api.UsersController

如您所见，我专门在路由上设置命名空间，并且我将UseNamespaceFallback设置为false以避免冲突，但它们无论如何都会发生。 我怎样才能解决这个问题？

Answer 1

MyApp.Controllers.Api.v2.UsersController位于命名空间MyApp.Controllers.Api中。 所以在同一个命名空间中有两个UsersController 。

使用UseNamespaceFallback仅仅意味着如果v2命名空间中没有UsersController ，则检查以前的命名空间，因此设置它的值对非v2命名空间没有影响，即有问题的命名空间。

您应该能够将第一个命名空间更新为：

MyApp.Controllers.Api.v1.UsersController
// and then
MyApp.Controllers.Api.v2.UsersController

然后您可以更新命名空间参数：

namespaces: new[] { "MyApp.Controllers.Api.v1" },

Answer 2

我不知道为什么没有提到更多的地方，但显然System.Web.Http.Dispatcher.DefaultHttpControllerSelector （顾名思义，默认情况下解析控制器）不支持Namespaces数据令牌（或任何其他限制命名空间的方式）。 我能够通过向 WebApiContrib 添加 Nuget 引用并将我的API配置为在Global.asax.cs中使用NamespaceHttpControllerSelector来修复我的路由：

GlobalConfiguration.Configuration.Services.Replace(typeof(IHttpControllerSelector), new NamespaceHttpControllerSelector(GlobalConfiguration.Configuration));