MvcSiteMapProvider和dynamicNodeProvider出现问题

 <add name="MvcSiteMapProvider"
             type="MvcSiteMapProvider.DefaultSiteMapProvider, MvcSiteMapProvider"
             siteMapFile="~/Sitemap/SiteMap.sitemap"
             securityTrimmingEnabled="true"

             enableLocalization="true"
             scanAssembliesForSiteMapNodes="true"
             skipAssemblyScanOn=""
             attributesToIgnore="bling"
             nodeKeyGenerator="MvcSiteMapProvider.DefaultNodeKeyGenerator, MvcSiteMapProvider"
             controllerTypeResolver="MvcSiteMapProvider.DefaultControllerTypeResolver, MvcSiteMapProvider"
             actionMethodParameterResolver="MvcSiteMapProvider.DefaultActionMethodParameterResolver, MvcSiteMapProvider"
             aclModule="MvcSiteMapProvider.DefaultAclModule, MvcSiteMapProvider"
             siteMapNodeUrlResolver="MvcSiteMapProvider.DefaultSiteMapNodeUrlResolver, MvcSiteMapProvider"
             siteMapNodeVisibilityProvider="MvcSiteMapProvider.DefaultSiteMapNodeVisibilityProvider, MvcSiteMapProvider"

这是我的.sitemap文件

<?xml version="1.0" encoding="utf-8" ?>
<mvcSiteMap xmlns="http://mvcsitemap.codeplex.com/schemas/MvcSiteMap-File-2.0" enableLocalization="true">

    <mvcSiteMapNode title="Classifieds" controller="Classifieds" action="Index"  changeFrequency="Always" updatePriority="Normal">
        <mvcSiteMapNode title="Category" controller="Classifieds" action="ClassifiedSelection"  dynamicNodeProvider="MySite.Helpers.ClassifiedCatDynamicNodeProvider, MySite.Helpers" >
          <mvcSiteMapNode title="SpecificAd" controller="Classifieds" action="SpecificClassified" dynamicNodeProvider="MySite.Helpers.ClassifiedAdsDynamicNodeProvider, MySite.Helpers" >
            <mvcSiteMapNode title="Email Seller" controller="Classifieds" action="EmailSeller" />

        </mvcSiteMapNode>
      </mvcSiteMapNode>
    </mvcSiteMapNode>

</mvcSiteMap>

http://mvcsitemap.codeplex.com/wikipage?title=Dynamic%20sitemaps&version=1 )

我不能让网站地图工作在所有我得到一个值不能为空错误,每当我加载网页与网站地图。

请帮忙。