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http://localhost/ArticleSite/Articles/list/csharp
http://localhost/ArticleSite/Articles/list/java
http://localhost/ArticleSite/Articles/edit/csharp
http://localhost/Shopping/electronics/show/homeappliances
http://localhost/Shopping/electronics/show/mobiles
Advantages of Routing
Most often, we work on data driven
websites where data is categorized and stored. For example, if we are building a
shopping website we may have products in various categories like home
appliances, mobiles, Apparels, Jewels, Perfumes, etc. To build a list page to
display the products in a category, we will normally develop an asp.net page
that accepts the category ID as query string to populate the product list. For
example,
http://localhost/Shopping/productlist.aspx?CatID=C91E9918-BEC3-4DAA-A54B-0EC7E874245E
As you can see, the above URL is not
readable and descriptive to understand the purpose it is going to serve. When we
use routing in these scenarios we can make the URL more descriptive, readable,
predictable and most importantly search engine friendly. Something similar
to,
http://localhost/Shopping/electronics/show/mobiles
The above URL speaks itself i.e. it is
intended to display a list of mobile phones in electronics category.
Initially, the ASP.Net routing engine
is packed with the new ASP.Net MVC framework. Later, Microsoft shipped this
feature (System.Web.Routing namespace) with .Netframework 3.5 SP1 to work with
normal asp.net application.
Moving forward, we will implement a
simple routing mechanism in ASP.Net 3.5. In order to provide routing in asp.net
application, we need to first define routes and routing handler.
What is a Route?
A route is a format or pattern of URL
we define for application. The route can have placeholders and constant values.
The place holders will be replaced with the values that we supply in the URL
during processing.
For example,
{controller}/{action}/{Category} --
/products/list/cars or /product/list/phones
Articles/{action}/{Category} --
/Articles/list/jQuery, /Articles/edit/jQuery
As you can see above, the placeholders
are normally placed in { } and constants (Articles) are defined between the
allowed delimiter /. The Routing engine will read place holder values, populate
it into a name/value pairs and make it available for processing throughout the
request.
Read this msdn article to know more about defining routes and adding
constraints.
A Route is
processed and resolved to a virtual path by a route handler. Once we defined our
routes, we need to define our route hander to handle the request that follows
the route pattern.
What is a RouteHandler?
A RouteHandler is an object that
returns the instance of the actual ASP.NET page or HTTP Handler to complete the
processing for the URL requested. A RouteHandler class should inherit the
System.Web.Routing.IRouteHandler interface and implement GetHttpHandler()
method.
To summarize, in order to work with
routing, one should define Routes and RouteHandler to handle incoming request. A
route should be registered with a Route handler in Application_Start event of
the application object i.e. in global.asax file and it should be added to
RouteTable object. Once registered, the incoming request is intercepted by the
routing module; it matches the request URL with the registered routes and
forwards them to the registered RouteHandler to complete the processing. The
routing module is registered in HttpModules section of the
web.config.
To understand the routing in ASP.Net,
we will build a very simple asp.net application that displays list of employees
in different departments.
Steps
1. Create a new Asp.Net website and include a new SqlExpress database in App_Data Folder.
2. Create 2 new tables called Employees and Department with some relevant columns.
Something like below image,
In this example, we will
create a simple route that has the department id of the employees in the URL
instead of passing it as query string. Refer below pattern,
"Employees/{Dept}/{action}.aspx"
The valid URL’s for the above routes
may be,
Employees/Sales/list.aspx
Employees/HR/list.aspx
Employees/IT/edit.aspx
Employees/Sales/delete.aspx
As I said earlier, we need to first
create and register route to a route handler in Global.asax file. In order to
register RouteHandler, we need to create the route handler to handle the request
that has the url in the following route pattern
"Employees/{Dept}/{action}.aspx"
To do this, right click your solution
in solution explorer and include a class file. I have named it as
EmployeeRouteHandler. Import the routing namespace System.Web.Routing. Now,
inherit the class from IRouteHandler interface and implement GetHttpHanlder()
method, which should return the actual page or a handler to handle the request.
Refer the code below,
using System;
using
System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.Routing;
using System.Web.Compilation;
/// <summary>
/// Summary description for
EmployeeRouteHandler
/// </summary>
public class EmployeeRouteHandler:
IRouteHandler
{
public
EmployeeRouteHandler()
{
//
// TODO: Add constructor
logic here
//
}
public IHttpHandler
GetHttpHandler(RequestContext requestContext)
{
string DeptName =
requestContext.RouteData.Values["Dept"] as string;
HttpContext context =
HttpContext.Current;
context.Items.Add("Dept",
DeptName);
string action =
requestContext.RouteData.Values["action"] as string;
if(action.ToLower() ==
"list")
return
BuildManager.CreateInstanceFromVirtualPath("~/Default.aspx", typeof(Page)) as
Page;
else
return
BuildManager.CreateInstanceFromVirtualPath("~/Default.aspx", typeof(Page)) as
Page;
}
}
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