Ensure that HttpConfiguration.EnsureInitialized() is called in the application's startup code after

老项目升级碰到的问题， .net mvc4.0 长为.net mvc 5.0碰到。

解决方案：

在Global.asax 文件里的Application_Start方法后面，加上

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();

    WebApiConfig.Register(GlobalConfiguration.Configuration);
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    RouteConfig.RegisterRoutes(RouteTable.Routes);
    BundleConfig.RegisterBundles(BundleTable.Bundles); ConfigJson();

    GlobalConfiguration.Configuration.EnsureInitialized();
}