String Parameter in url

Question

Hy Guys, I have to pass in a method action a string parameter, because I want to implement a tags' search in my site with asp.net MVC but everytime in action it is passed a null value.

I post some code!

I try to create a personal route.

 routes.MapRoute(
            "TagsRoute",
            "Tags/PostList/{tag}",
            new {tag = "" }
        );

My RouteLink in a viewpage for each tag is:

<% foreach (var itemtags in item.tblTagArt) {%> 

    <%= Html.RouteLink(itemtags.Tags.TagName,"TagsRoute", 
        new {tag=itemtags.Tags.TagName})%>,    
<% } %>

My method action is:

 public ActionResult PostList(string tag)
    {
        if (tag == "")
        {
            return RedirectToAction("Index", "Home");
        }
        else
        {
            var articoli = artdb.GetArticoliByTag(tag);

            if (articoli == null)
            {
              return RedirectToAction("Index", "Home");
            }

            return View(articoli);
        }
    }

Problem is value tag that's always null, and so var articoli is always empty!

Probably my problem is tag I have to make a route contrainst to my tag parameter.

Anybody can help me?

N.B I am using ASP.NET MVC 1.0 and not 2.0!

Hi, how about if (String.IsNullOrEmpty(tag)) instead of if (tag == "")? — Trimack
– Trimack, Commented May 8, 2010 at 11:03

Darin Dimitrov · Accepted Answer · 2010-05-08 13:58:38Z

4

Where did you put this custom route definition? It should be before the Default one.

public static void RegisterRoutes(RouteCollection routes)
{
    routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

    routes.MapRoute(
        "TagsRoute",
        "Tags/PostList/{tag}",
        new { controller = "Tags", action = "PostList", id = UrlParameter.Optional }
    );

    routes.MapRoute(
        "Default",
        "{controller}/{action}/{id}",
        new { controller = "Users", action = "Index", id = UrlParameter.Optional }
    );
}

answered May 8, 2010 at 13:58

Darin Dimitrov

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4 Comments

Ivan90 Over a year ago

Thanks! It does work :) So, the order of maproute is very important? And why, did in this way it does work? Thanks :)

Darin Dimitrov Over a year ago

Yes, the order is important. Routes are evaluated in the order they are declared and the first to match the request url is executed.

Ivan90 Over a year ago

Ok, I understand, but this it explain because tag value is always null even if in reality I always pass it with RouteLink? And when it necessary specified an IrouteContraint? and If I pass a double? So RouteContraint it's useful only if we must specified the form of the parameter but not the type?

EvgeniyK Over a year ago

Did you mean 'tag = UrlParameter.Optional' in first MapRoute?

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