Url.Action reuses route data when I don't want it to - asp.net

Question

In my layout page, the links to the main sections that make up my site are rendered with a call like this:
#SiteSectionLink("index", "blog", "blog")
Where SiteSectionLink is a helper that looks like this:
#helper SiteSectionLink(string action, string controller, string display)
{
<li>
<h1>
<a class="site-section" href="#Url.Action(action, controller)">#display</a></h1>
</li>
}
On the actual blog page, all links also refer to the "Index" action but also specify either a date parameter (such as "blog/4-2011" or "blog/2010") that is used to filter the posts by a date period. In addition to that, there's also an optional postID parameter that is used to refer to a specific post.
To accomplish that, I have the following routes:
routes.MapRoute(
"Blog",
"blog/{date}/{postID}",
new
{
controller = "blog",
action = "index",
date = UrlParameter.Optional,
postID = UrlParameter.Optional
}
);
routes.MapRoute(
"Default", // Route name
"{controller}/{action}/{id}", // URL with parameters
new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
);
Now, the problem is that when I have clicked a link that is something like "blog/11-2010" or "blog/11-2010/253" then the link in my layout page that refers to my blog in general now also refers to that same URL when I want it to just link to "blog/", not "blog/11-2010".
If I change the SiteSectionLink helper to explicitly pass in null for date and postID like this:
<a class="site-section" href="#Url.Action(action, controller,
new { date = (string)null, postID = (int?)null})">#display</a></h1>
The current route values are still used but now it looks like "blog?date=11-2010".
I saw this similar question but the accepted answer doesn't work for me, and I don't use ActionLink in the first place and I suspect that ActionLink would use Url.Action under the hood.

Answer 1

While the issue you are experiencing is not quite the behavior detailed by Phil Haack in this blog post regarding a bug with MVC3 routing and a route with two optional parameters, I would suggest applying the fix described in Phil's post.
I also would suggest never creating a route with two optional parameters, and instead follow the pattern of breaking the desired routing into two separate routes.

Answer 2

Yes Url.Action method puts the parameters in the querystring.
You can change your helper like this:
#helper SiteSectionLink(string action, string controller, string display, string date = null, string id=null)
{
<li>
#if (date == null)
{
<h1><a class="site-section" href="~/blog/#controller/#action">#display</a></h1> // simple workaround or better use P. Haack workaround
}
else
{
<h1><a class="site-section" href="#Url.RouteUrl("blog", new { action = #action, controller = #controller, date = #date, id = #id })">#display</a></h1>
}
</li>
}
So you can use SiteSelectionLink like these:
#SiteSectionLink("Index", "Blog", "test", "2011", "4")
#SiteSectionLink("Index", "Blog", "test2", "2011")
#SiteSectionLink("Index", "Blog", "test3")