Asp.net css结构伪类

我想在asp.net中获得我菜单的第一级来更改边框底色，第一级中的每个项目都有边框底色 这是生成的html

<div id="menu">


<div class="PrettyMenu">
    <div class="AspNet-Menu-Horizontal">
        <ul class="AspNet-Menu">
            <li class="AspNet-Menu-WithChildren">
                <a href="javascript:__doPostBack('ctl00$Menu1','bRessources Humaines')" class="AspNet-Menu-Link">G.R.H</a>
                <ul>
                    <li class="AspNet-Menu-WithChildren">
                        <a href="javascript:__doPostBack('ctl00$Menu1','bRessources Humaines\\Employés')" class="AspNet-Menu-Link">
                            Employés</a>
                        <ul>
                            <li class="AspNet-Menu-Leaf">
                                <a href="employe/listeemployee.aspx" class="AspNet-Menu-Link">
                                    Employé</a>
                            </li>
                            <li class="AspNet-Menu-Leaf">
                                <a href="employe/fonction.aspx" class="AspNet-Menu-Link">
                                    Fonctions</a>
                            </li>
                        </ul>
                    </li>
                    <li class="AspNet-Menu-WithChildren">
                        <a href="javascript:__doPostBack('ctl00$Menu1','bRessources Humaines\\Formations')" class="AspNet-Menu-Link">
                            Formations</a>
                        <ul>
                            <li class="AspNet-Menu-Leaf">
                                <a href="Formation/Listeformation.aspx" class="AspNet-Menu-Link">
                                    Planning</a>
                            </li>
                            <li class="AspNet-Menu-Leaf">
                                <a href="Formation/Listedemandeformation.aspx" class="AspNet-Menu-Link">
                                    Demandes de formation</a>
                            </li>
                        </ul>
                    </li>
                    <li class="AspNet-Menu-Leaf">
                        <a href="employe/RemplacerPersonne.aspx" class="AspNet-Menu-Link">
                            Remplacer personne</a>
                    </li>
                </ul>
            </li>
            <li class="AspNet-Menu-WithChildren">
                <a href="javascript:__doPostBack('ctl00$Menu1','bDocumentations')" class="AspNet-Menu-Link">
                    Documentation</a>
                <ul>
                    <li class="AspNet-Menu-WithChildren">
                        <a href="javascript:__doPostBack('ctl00$Menu1','bDocumentations\\Documents Internes')" class="AspNet-Menu-Link">
                            Documents internes</a>
                        <ul>
                            <li class="AspNet-Menu-Leaf">
                                <a href="Documentation/DocumentInterne.aspx" class="AspNet-Menu-Link">
                                    Mes documents internes</a>
                            </li>
                            <li class="AspNet-Menu-Leaf">
                                <a href="Documentation/Fiche_DocumentPrime.aspx" class="AspNet-Menu-Link">
                                    DI périmés</a>
                            </li>
                        </ul>
                    </li>
                    <li class="AspNet-Menu-Leaf">
                        <a href="Documentation/boite_dialogue.aspx" class="AspNet-Menu-Link">
                            Boîte de dialogue</a>
                    </li>
                    <li class="AspNet-Menu-Leaf">
                        <a href="Documentation/Fiche_Document.aspx" class="AspNet-Menu-Link">
                            Création, Modification</a>
                    </li>
                </ul>
            </li>
            <li class="AspNet-Menu-WithChildren">
                <a href="javascript:__doPostBack('ctl00$Menu1','bAudits')" class="AspNet-Menu-Link">
                    Audits</a>
                <ul>
                    <li class="AspNet-Menu-Leaf">
                        <a href="Audit/listeaudite.aspx" class="AspNet-Menu-Link">
                            Audits1</a>
                    </li>
                    <li class="AspNet-Menu-Leaf">
                        <a href="Audit/AuditeurExterne.aspx" class="AspNet-Menu-Link">
                            Auditeurs externes</a>
                    </li>
                </ul>
            </li>
            <li class="AspNet-Menu-WithChildren">
                <a href="javascript:__doPostBack('ctl00$Menu1','bActions')" class="AspNet-Menu-Link">
                    Actions</a>
                <ul>
                    <li class="AspNet-Menu-Leaf">
                        <a href="action/listeaction.aspx" class="AspNet-Menu-Link">
                            Actions1</a>
                    </li>
                    <li class="AspNet-Menu-Leaf">
                        <a href="action/listedemandeaction.aspx" class="AspNet-Menu-Link">
                            Demandes d'actions</a>
                    </li>
                </ul>
            </li>
                <a href="javascript:__doPostBack('ctl00$Menu1','bGénérateur de rapports')" class="AspNet-Menu-Link">
                    Générateur</a>
                <ul>
                    <li class="AspNet-Menu-Leaf">
                        <a href="Generateur/generateur.aspx" class="AspNet-Menu-Link">
                            Création</a>
                    </li>
                    <li class="AspNet-Menu-Leaf">
                        <a href="Generateur/generateur_edition.aspx" class="AspNet-Menu-Link">
                            Edition</a>
                    </li>
                </ul>
            </li>
        </ul>
    </div>
</div>


</div>

但它会将第一级物品的所有边框变为红色

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请提供任何帮助

您可以使用>combinator以元素的直接子元素为目标。[]

.AspNet菜单>li>.AspNet菜单链接{ 边框颜色：红色； 边框宽度：0px 0px 2px 0px； 边框样式：实心； }

.AspNet-Menu-Link:nth-child(1) 
{
 border-bottom-color: red;
}