就我而言，在花了将近 30 分钟试图解决问题后，我找到了导致它的原因:

In my case after spending almost 30 minutes trying to fix the problem, I found what was causing it:

我在 WebApiConfig.cs 中定义的路由是这样的:

My route defined in WebApiConfig.cs was like this:

config.Routes.MapHttpRoute(
    name: "ControllersApi",
    routeTemplate: "{controller}/{action}"
);

它应该是这样的:

config.Routes.MapHttpRoute(
    name: "ControllersApi",
     routeTemplate: "api/{controller}/{action}/{id}",
        defaults: new { id = RouteParameter.Optional }
);

如您所见，它干扰了 RouteConfig.cs 中定义的标准路由.

as you see it was interfering with the standard route defined in RouteConfig.cs.