asp.net-mvc – ASP.NET MVC4路由问题

我已经搜索了Stack多年,阅读了MSDN文档并使用了Bing,但是看不出为什么这不起作用！我在路线下面有相关的代码.名为Browse的路由工作得很好,但Details路由的productCode参数总是等于零.如果我制作任何mods,我会继续获得“找不到资源”404页面.

' Lives in controller called 'Details'
' Usage: site.com/details/abc123
Function Index(productCode As String) As ActionResult

' Lives in controller called 'Browse'    
' Usage: site.com/browse/scifi/2
Function Index(genre As String,Optional page As Integer = 1) As ActionResult

路线是：

routes.MapRoute( _
        "Browse",_
        "{controller}/{genre}/{page}",_
        New With {.controller = "Browse",.action = "Index",.id = UrlParameter.Optional,.page = UrlParameter.Optional}
    )

    routes.MapRoute( _
        "Details",_
        "details/{productCode}",_
        New With {.controller = "Details",.action = "Info",.productCode = UrlParameter.Optional}
    )