Dealing with varying number of route segments in ASP.NET MVC
Most of the times the ASP.NET MVC routes consists of known number of
segments. For example, consider the default route pattern defined by ASP.NET
MVC:
routes.MapRoute(
name: "Default",
url: "{controller}/{action}/{id}",
defaults: new { controller = "Home",
action = "Index",
id = UrlParameter.Optional }
);
Here, the route consists of three segments namely controller, action and an
optional id. This works well for many applications. However, at times you may
not have idea about the exact number of route segments involved. Consider the
following example.
Suppose you are building an application that shows the population in one or
more cities of a country. So, you need to pass the country name and one or more
cities as a part of the URLs. Some sample URLs are given below:
/home/getdata/USA/Chicago
/home/getdata/USA/Chicago/Houston
/home/getdata/USA/Seattle/Boston/Tampa
As you can see from the above URLs, one could specify any number of cities in
the route segments. Obviously you can't have a route pattern with a known number
of segments. Luckily, ASP.NET MVC allows you to use what is often called
catch-all route parameter. Let's see how it can be used in this situation.
Create a new ASP.NET MVC application and open its RouteConfig.cs file. Then
add the following MapRoute() call after the default route pattern.
routes.MapRoute(
name: "CatchAll",
url: "{controller}/{action}/
{country}/{*cities}",
defaults: new { controller = "Home",
action = "GetData" }
);
Notice that the route pattern consists of four parameters namely controller,
action, country and *cities. The *cities does the trick for us. This catch-all
parameter indicates that any number of route segments can follow the country
segment. Also notice that the route is configured to be handled by the GetData()
action of the HomeController. The catch-all parameter must appear as the last
segment of a route.
The GetData() action looks like this:
public ActionResult GetData(string country,string cities)
{
string[] cityArray = cities.Split('/');
ViewBag.Country = country;
ViewBag.Cities = cityArray;
return View();
}
The GetData() action takes two parameters - country and cities. Note that
names of these parameters must match with the names of the route parameters
defined in the RouteConfig.cs.
Capturing and using the country parameter is quite straightforward. The
cities parameter could be a single city or multiple cities in the form
city1/city2/city3. So, you need to split this string to get an array. Once you
do that you are free to process the country and city values as per the
application's logic. In this case you simply pass them to the GetData view
through the ViewBag.
The Index view looks like this:
<body>
<h1>
<a href="/home/getdata/USA/Chicago">USA - Chicago</a>
</h1>
<h1>
<a href="/home/getdata/USA/Chicago/Houston">
USA - Chicago and Houston
</a>
</h1>
<h1>
<a href="/home/getdata/USA/Seattle/Boston/Tampa">
USA - Seattle, Boston and Tampa
</a>
</h1>
</body>
The Index view simply renders a few links with USA as the country and some
combination of cities.
The GetData view is shown below:
<body>
<h1>@ViewBag.Country</h1>
@foreach(string city in ViewBag.Cities)
{
<h2>@city</h2>
}
</body>
The GetData view simply displays the country received in the controller and
also a list of cities received from the route segments.
The following figure shows a sample run of the application.
Notice how the URL segments and the output of the view shows the country and
cities.
That's it! Keep coding !!