获取首要网站的第一级子网站

protected override void Render(HtmlTextWriter writer)
        {
string strNavigation = string.Empty;

using (SPSite spSite = new SPSite(SPContext.Current.Site.Url))
            {                
                SPWeb spWeb = spSite.OpenWeb();
foreach (SPNavigationNode spNavNode in spWeb.Navigation.TopNavigationBar)
                {
//子站点的url                       
                    string strurl = spNavNode.Url;                       
//子站点的name                       
                    string strname = spNavNode.Title; 
                }
            }
        }