Two level horizontal menu for ASP.NET06 Nov 2009
When I decided to have a 2-level horizontal menu for my professional webpage in ASP.NET, it came as a surprise to me that this wasn’t completely straightforward. I expected the standard ASP menu control to support this, but found out that this wasn’t the case.
The one issue I had with his implementation, however, was that the second level menu uses multiple data sources. The Master Page handles the top-level menu, but each page contains a reference to the specific datasource used to populate the sub-menu. As a result, if you decide to add a page, you need to manually add to that page some code to define what sub-menu should show up, which is cumbersome.
The ideal solution for a lazy developer like me would be to have all the menus handled in the Master Page, so that when you add a new page to your website, you just need to add it to the Sitemap, and the right menu and sub-menu shows up.
After some tinkering about, I figured out how to get this done. The trick is to use the Attribute StartingNodeOffset of the SiteMapDataSource.
I used the CSSFriendlyModified.dll Peter presents in his code sample, but modified the MasterPage, which looks like this:
<div id="Navigation"> <asp:SiteMapDataSource ID="SiteMapMain" runat="server" showStartingNode="False"/> <div class="MainMenuSection"> <asp:Menu ID="MainMenu" runat="server" DataSourceID="SiteMapMain" MaximumDynamicDisplayLevels="0" Orientation="Horizontal"> </asp:Menu> </div> <asp:SiteMapDataSource ID="SiteMapSecondLevel" runat="server" showStartingNode="False" StartingNodeOffset="1"/> <div class="SecondaryMenuSection"> <asp:Menu ID="SecondaryMenu" runat="server" DataSourceID="SiteMapSecondLevel" Orientation="Horizontal" /> </div> </div>
The first block (SiteMapMain and MainMenu) declare what DataSource to use for the top-level menu (the SiteMap), and is pretty much identical to Peter’s code.
The second block declares a second DataSource (SiteMapSecondLevel), which hooks up to the SiteMap. Note the difference with the first DataSource: StartingNodeOffset is set to 1, which essentially tells the DataSource to look one level down in the nodes hierarchy of the SiteMap. The sub-menu “SecondaryMenu” simply uses that DataSource, regardless of the page.
As a result, now there is no need to add any code for pages to handle the second level menu. As long as a page is listed in the SiteMap, and hooked to the MasterPage, it will automatically populate the second level menu with the nodes that are listed under the top-level node. You can see that in action on this page, for instance. Enjoy!
And, give credit where credit is due - thanks a million for Peter Kellner – his code was a total life-saver.