Hi there,
Assuming you do have all required references for Bootstrap 3.3.7 (js and css), as well as JQuery, just like Matias Lopez mentioned; the following code example may offer some help.
It depicts a menu with three items, where the last one is a sub-menu. For this particular case, LinkButtons were used, but if your intent is plain navigation, then you can use the HTML, and just complete the
href="...". Link tags Ids may also be unnecessary in such case.
<div id="MnuCliente" runat="server" class ="collapse navbar-collapse" >
<ul class="nav navbar-nav">
<li><asp:LinkButton id="Mnu00" runat="server" Text="Datos Cliente" OnClick="Link_Click" /></li>
<li><asp:LinkButton id="Mnu01" runat="server" Text="Operaciones" OnClick="Link_Click" /></li>
<li class="dropdown-submenu">
<a href="#" class="dropdown-toggle" data-toggle="dropdown">Documentosclass="caret"></a>
<ul class="dropdown-menu">
<li><asp:LinkButton id="Mnu02" runat="server" Text="Vigentes" OnClick="Link_Click" /></li>
<li><asp:LinkButton id="Mnu03" runat="server" Text="Morosos" OnClick="Link_Click" /></li>
<li><asp:LinkButton id="Mnu04" runat="server" Text="Cancelados" OnClick="Link_Click" /></li>
<li><asp:LinkButton id="Mnu05" runat="server" Text="Prorrogados" OnClick="Link_Click" /></li>
<li><asp:LinkButton id="Mnu06" runat="server" Text="Protestados" OnClick="Link_Click" /></li>
<li><asp:LinkButton id="Mnu07" runat="server" Text="Excedentes" OnClick="Link_Click" /></li>
</ul>
</li>
</ul>
</div>
<div id="MnuClient" class="collapse navbar-collapse">
<ul class="nav navbar-nav">
<li><a id="Mnu00" href="...">Datos Cliente</a></li>
<li><a id="Mnu01" href="...">Operaciones</a></li>
<li class="dropdown-submenu">
<a href="#" class="dropdown-toggle" data-toggle="dropdown">Documents^__b class="caret"></a>
<ul class="dropdown-menu">
<li><a id="Mnu02" href="...">Vigentes</a></li>
<li><a id="Mnu03" href="...">Morosos</a></li>
<li><a id="Mnu04" href="...">Cancelados</a></li>
<li><a id="Mnu05" href="...">Prorrogados</a></li>
<li><a id="Mnu06" href="...">Protestados</a></li>
<li><a id="Mnu07" href="...">Excedentes</a></li>
</ul>
</li>
</ul>
</div>
Cheers!