ASP.NET MVC报错: Multiple types were found that match the controller named

当使用ASP.NET MVC的Area功能时，出现了这样的错误：
Multiple types were found that match the controller named 'Home'. This can happen if the route that services this request ('{controller}/{action}/{id}') does not specify namespaces to search for a controller that matches the request. If this is the case, register this route by calling an overload of the 'MapRoute' method that takes a 'namespaces' parameter.
The request for 'Home' has found the following matching controllers:
MvcTest.Web.Controllers.HomeController 

MvcTest.Web.Areas.TestArea.Controllers.HomeController

这是因为你定义了两个HomeController（默认的一个，Area中一个），系统无法确定你默认的Controller=“Home”到底是哪一个。 

只需要在你的global.asax中的routes.MapRoute()方法中，添加一个默认的命名空间，如：
       public static void RegisterRoutes(RouteCollection routes) {
           routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
           routes.MapRoute(
               "Default",                                              // Route name
               "{controller}/{action}/{id}",                           // URL with parameters
               new { controller = "Home", action = "Index", id = "" },  // Parameter defaults
               new string[] { "MvcTest.Web.Controllers" }
           );
       }
注意上面的new string[] { "MvcTest.Web.Controllers" }参数，在Area的对应AreaRegistration.cs类中的routes.MapRoute方法中，也加入这个参数，不同的是字符串要改写成Area的Controller对应的命名空间，如new[] { "MvcTest.Web.Areas.TestArea.Controllers" }