asp.net-TreeView —所选节点样式不会出现在所选节点上

我的代码是：

            <asp:TreeView ID="TreeViewCategories" runat="server" ExpandDepth="0" Style="min-height: 200px;
                max-height: 500px;" LineImagesFolder="~/TreeLineImages" NodeIndent="0" LeafNodeStyle-CssClass="LeafNodesStyle"
                CssClass="TreeView" NodeStyle-CssClass="NodeStyle" ParentNodeStyle-CssClass="ParentNodeStyle"
                RootNodeStyle-CssClass="RootNodeStyle" SelectedNodeStyle-CssClass="SelectedNodeStyle"
                LeafNodeStyle-Width="100%" NodeStyle-Width="100%" ParentNodeStyle-Width="100%"
                RootNodeStyle-Width="100%" Font-Size="12pt">
                <Nodes>
                    <asp:TreeNode Text="All Items" SelectAction="Expand" PopulateOnDemand="True" Value="All Items" />
                </Nodes>
            </asp:TreeView>

的CSS

.TreeView  
{
    border-bottom:1px dotted #B2B2B2 !important;
}

.TreeView div
{
    margin-left:5px;
}

.TreeView table
{
    border-top:1px dotted #B2B2B2 !important;
}

.TreeView div table
{
    border-bottom:none !important;
    border-top:none !important;
}

.TreeView table td
{
    padding:2px 0;
}

.LeafNodesStyle 
{

}

.RootNodeStyle 
{

}

/* ALL ELEMENTS */

.NodeStyle 
{

}

.ParentNodeStyle 
{
    /*background:yellow;*/
}

.SelectedNodeStyle { font-weight: bold; color:#6799D1; display:block; padding:2px 0 2px 3px; }

所以我看到(带有萤火虫)我选择的节点出现了Visited style,node style,leaf style但不是Selected Node style