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" }