Mixing ASP.NET Webforms and ASP.NET MVC

Ever since Microsoft started working on the ASP.NET MVC framework, one of the primary concerns was the framework's ability to re-use as many features as possible from ASP.NET Webforms. In this article by Maarten Balliauw, we will see how we can mix ASP.NET Webforms and ASP.NET MVC in one application and how data is shared between both these technologies.

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Not every ASP.NET MVC web application will be built from scratch. Several projects will probably end up migrating from classic ASP.NET to ASP.NET MVC. The question of how to combine both technologies in one application arises—is it possible to combine both ASP.NET Webforms and ASP.NET MVC in one web application? Luckily, the answer is yes.

Combining ASP.NET Webforms and ASP.NET MVC in one application is possible—in fact, it is quite easy. The reason for this is that the ASP.NET MVC framework has been built on top of ASP.NET. There's actually only one crucial difference: ASP.NET lives in System.Web, whereas ASP.NET MVC lives in System.Web, System.Web.Routing, System.Web.Abstractions, and System.Web.Mvc. This means that adding these assemblies as a reference in an existing ASP.NET application should give you a good start on combining the two technologies.

Another advantage of the fact that ASP.NET MVC is built on top of ASP.NET is that data can be easily shared between both of these technologies. For example, the Session state object is available in both the technologies, effectively enabling data to be shared via the Session state.

Plugging ASP.NET MVC into an existing ASP.NET application

An ASP.NET Webforms application can become ASP.NET MVC enabled by following some simple steps. First of all, add a reference to the following three assemblies to your existing ASP.NET application:

• System.Web.Routing
• System.Web.Abstractions
• System.Web.Mvc

After adding these assembly references, the ASP.NET MVC folder structure should be created. Because the ASP.NET MVC framework is based on some conventions (for example, controllers are located in Controllers), these conventions should be respected. Add the folder Controllers, Views, and Views | Shared to your existing ASP.NET application.

The next step in enabling ASP.NET MVC in an ASP.NET Webforms application is to update the web.config file, with the following code:

< ?xml version="1.0"?>
<configuration>
  <system.web>
    <compilation debug="false">
      <assemblies>
        <add assembly="System.Core, Version=3.5.0.0, Culture=neutral,
                       PublicKeyToken=B77A5C561934E089"/>
        <add assembly="System.Web.Extensions,
                       Version=3.5.0.0, Culture=neutral,
                       PublicKeyToken=31BF3856AD364E35"/>
        <add assembly="System.Web.Abstractions,
                       Version=3.5.0.0, Culture=neutral,
                       PublicKeyToken=31BF3856AD364E35"/>
        <add assembly="System.Web.Routing,
                       Version=3.5.0.0, Culture=neutral,
                       PublicKeyToken=31BF3856AD364E35"/>
      </assemblies>
    </compilation> 
    <pages>
      <namespaces>
        <add namespace="System.Web.Mvc"/>
        <add namespace="System.Web.Mvc.Ajax"/>
        <add namespace="System.Web.Mvc.Html" />
        <add namespace="System.Web.Routing"/>
        <add namespace="System.Linq"/>
        <add namespace="System.Collections.Generic"/>
      </namespaces>
    </pages>
    <httpModules>
      <add name="UrlRoutingModule"
           type="System.Web.Routing.UrlRoutingModule,
                 System.Web.Routing, Version=3.5.0.0,
                 Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
    </httpModules>
  </system.web>
</configuration>

Note that your existing ASP.NET Webforms web.config should not be replaced by the above web.config! The configured sections should be inserted into an existing web.config file in order to enable ASP.NET MVC.

There's one thing left to do: configure routing. This can easily be done by adding the default ASP.NET MVC's global application class contents into an existing (or new) global application class, Global.asax.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Routing;

namespace MixingBothWorldsExample
{
    public class Global : System.Web.HttpApplication
    {
        public static void RegisterRoutes(RouteCollection routes)
        {
            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
            routes.IgnoreRoute("{resource}.aspx/{*pathInfo}");
            routes.MapRoute(
               "Default",
// Route name
               "{controller}/{action}/{id}",
// URL with parameters
               new { controller = "Home", action = "Index", id = "" }
// Parameter defaults
                );
        }
        protected void Application_Start()
        {
            RegisterRoutes(RouteTable.Routes);
        }
    }
}

This code registers a default ASP.NET MVC route, which will map any URL of the form /Controller/Action/Idinto a controller instance and action method. There's one difference with an ASP.NET MVC application that needs to be noted—a catch-all route is defined in order to prevent a request for ASP.NET Webforms to be routed into ASP.NET MVC. This catch-all route looks like this:

routes.IgnoreRoute("{resource}.aspx/{*pathInfo}");

This is basically triggered on every request ending in .aspx. It tells the routing engine to ignore this request and leave it to ASP.NET Webforms to handle things.

With the ASP.NET MVC assemblies referenced, the folder structure created, and the necessary configurations in place, we can now start adding controllers and views. Add a new controller in the Controllers folder, for example, the following simpleHomeController:

using System.Web.Mvc;
namespace MixingBothWorldsExample.Controllers
{
    public class HomeController : Controller
    {
        public ActionResult Index()
        {
            ViewData["Message"] = "This is ASP.NET MVC!";
            return View();
        }
    }
}

The above controller will simply render a view, and pass it a message through the ViewData dictionary. This view, located in Views | Home | Index.aspx, would look like this:

<%@ Page Language="C#"
    AutoEventWireup="true"
    CodeBehind="Index.aspx.cs"
    Inherits="MixingBothWorldsExample.Views.Home.Index" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title></title>
</head>
<body>
    <div>
        <h1><%=Html.Encode(ViewData["Message"]) %></h1>
    </div>
</body>
</html>

The above view renders a simple HTML page and renders the ViewData dictionary's message as the page title.