Jul 8 2010

Using MVCContrib glue to bring Visual Basic WebForms and C# MVC together

Category: ASP.NET | MVCMatt @ 16:14

While I’m digging my new job, I’ve found myself in the less-than-desirable situation of having to work with WebForms again.  After working almost exclusively with ASP.NET MVC for the better part of three years, the inadequacies of WebForms seem even more prominent.  While running MVC and WebForms in the same applications is easy enough, we’re facing an added complication: our WebForms application was written in Visual Basic.  While you can’t mix-and-match C# MVC and VB WebForms within the same application directly, you can leverage MVCContrib’s Portable Areas to bring the two together, which is what I’ll show you how to do in this post.

Giving credit where credit is due, Jeffery Palermo already described how you can leverage MVCContrib’s Portable Areas within a WebForms application.  Unfortunately, his sample doesn’t work (it appears to depend on an older MVC 2 CTP), and his post omits several important details.  Jeffery’s post also focuses on the creation of reusable modules whereas my interest is bringing C# into our VB project as seamlessly as possible.  Hopefully this guide, even though it’s focus is on bridging the C#-VB divide, will be useful to anyone that’s envious of MVC but stuck with a substantial amount of WebForms code.

Create a new solution

To get started, let’s go ahead and create a new empty solution in Visual Studio 2010.

VisualStudioNewProject

Next, add a Visual Basic WebForms application.  When you run the application, you should see something like this:

VbWebFormsHome

Note that I modified my master page to make it clear that the master page is a WebForms master page.  You’ll understand why later. 

Add MVC Support

As I mentioned, there’s plenty of information on the web about adding MVC support to an existing WebForms application.  The two play nicely side-by-side in the same project.  First, add references to the required assemblies: System.Web.Mvc, System.Web.Routing, and System.Web.Abstractions.  The last one is probably not strictly required, but I added it anyway. This is also a good time to go ahead and add a reference to MVCContrib.  Note that for the approach I’m going to describe to work, you will need to use a build based on the trunk and not the older release build available from CodePlex.  You can pick up a nightly build from the MVCContrib TeamCity build server (be sure to grab artifacts from a successful build).

MvcContribTeamCity

Next, you need to update your web.config file.  Replace the default compilation section with the following:

<compilation debug="true" targetFramework="4.0">
    <assemblies>
        <add assembly="System.Web.Abstractions, Version=4.0.0.0, 
             Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
        <add assembly="System.Web.Routing, Version=4.0.0.0, 
             Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
        <add assembly="System.Web.Mvc, Version=2.0.0.0, 
             Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
    </assemblies>
</compilation>

Also add a pages element with the namespaces shown:

<pages>
    <namespaces>
        <add namespace="System.Web.Mvc"/>
        <add namespace="System.Web.Mvc.Ajax"/>
        <add namespace="System.Web.Mvc.Html"/>
        <add namespace="System.Web.Routing"/>
    </namespaces>
</pages>

This step probably isn’t necessary (depends on how you are deploying your application), but for good measure, go ahead and add the MVC HTTP handler and a binding redirect for MVC 1:

<httpHandlers>
    <add verb="*" path="*.mvc" 
        validate="false" type="System.Web.Mvc.MvcHttpHandler,
        System.Web.Mvc, Version=2.0.0.0, Culture=neutral, 
        PublicKeyToken=31BF3856AD364E35"/>
</httpHandlers>
<runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
        <dependentAssembly>
            <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" />
            <bindingRedirect oldVersion="1.0.0.0" newVersion="2.0.0.0" />
        </dependentAssembly>
    </assemblyBinding>
</runtime>

Next up, we need to add some code in our Global.asax file:

Shared Sub RegisterRoutes(ByVal routes As RouteCollection)
    routes.IgnoreRoute("{resource}.axd/{*pathInfo}")

    ' MapRoute takes the following parameters, in order:
    ' (1) Route name
    ' (2) URL with parameters
    ' (3) Parameter defaults
    routes.MapRoute( _
     "Default", _
     "{controller}/{action}/{id}", _
     New With {.controller = "Home", .action = "Index", .id = UrlParameter.Optional} _
    )

End Sub

Sub Application_Start()
    AreaRegistration.RegisterAllAreas()

    PortableAreaRegistration.RegisterEmbeddedViewEngine()

    RegisterRoutes(RouteTable.Routes)
End Sub

The RegisterRoutes procedure is pretty standard, and AreaRegistration.RegisterAllAreas is boiler-plate MVC 2.0 stuff.  The other bit is important though: PortableAreaRegistration.RegisterEmbeddedViewEngine will register a special view engine that allows the application to consume Portable Areas.

The final thing we need to do is add some special folders that are needed by MVC: the Areas folder and the Views folder.  For now, go ahead and add a view master page at ‘~/Views/Shared/Site.master’.  I’d recommend copying both the Views and Areas folders from an existing ASP.NET MVC application (be sure to remove any of the views you don’t need, but save the Site.master one).  Once you’re finished, you should have a structure like this:

VbProjectCurrentState

At this point, the WebForms project is ready to consume our C# ASP.NET MVC Portable Area.  All we need to do is create one!

Creating a Portable Area

Most people recommend that you create a regular class library to serve as the host of your portable area, but there are some disadvantages to that approach.  First, you will have to re-add all the necessary MVC references in order to build controllers and views.  Second, you will lose all the Visual Studio tooling for MVC (as well as Resharper extensions for MVC projects).  In light of that, I recommend adding a regular-old ASP.NET MVC 2 (C#) application to your solution.  An MVC project is essentially a web application project, which means it produces a single DLL that you can reference from another application. 

After adding your MVC 2 project, you can remove all of the following: web.config files, Global.asax, views (but leave ‘~/Views/Shared/Site.master’ for now), controllers, models, script files, and CSS files. Save your project at this point, then unload it so that you can edit it. 

Edit project file, and add the following line to end of script before closing ‘project’ tag:

<Target Name="BeforeBuild">
  <ItemGroup>
    <EmbeddedResource Include="**\*.aspx;**\*.ascx;**\*.gif;**\*.css;**\*.js;**\*.png;**\*.jpg" />
  </ItemGroup>
</Target>

One of the requirements for building a Portable Area is that the views and any resources they depend on must be embedded in the assembly.  You can do this manually using the Properties pane in Visual Studio, but it’s easy to forget this critical step.  The MSBuild snippet above automatically embeds your views and any common content files. 

With your project file now modified, go ahead and reload it, then add a reference to MVCContrib.  We’ll add a “HelloWorld” controller to our project:

public class HelloWorldController : Controller
{
    public ViewResult Index()
    {
        return View();
    }

}

And we’ll create the corresponding view for our Index action:

<%@ Page Title="Hello from C#!" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage" %>

<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">
    Hello from C#!
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

    <h2>Hello, World!</h2>
    <p>This is a view from a portable area created in C#!</p>
    <p>The current time is <%=DateTime.Now.ToShortTimeString() %></p>

</asp:Content>

When creating the view, go ahead and specify the master, but note that at runtime the view will actually use the master from the parent project, not the Portable Area project.  We left the master view in the Portable Area project so that the views we create will have the correct content placeholder IDs (more on this later). 

The last thing we need to do to complete our portable area is add a registration class:

public class HelloWorldRegistration : PortableAreaRegistration
{
    public override string AreaName
    {
        get { return "HelloWorld"; }
    }

    public override void RegisterArea(AreaRegistrationContext context, IApplicationBus bus)
    {
        context.MapRoute("HelloWorld", "helloworld/{action}",
                         new { controller = "helloworld", action = "index" });

        RegisterAreaEmbeddedResources();
    }
}

Registration is fairly simple: we give our area a name, map a route to it, and call a base class method to register all the embedded resources for our Portable Area.

Visual Basic: Say Hello to C#!

So far we have a Visual Basic WebForms application and  C# MVC application, but the two aren’t playing in the same sandbox yet.  In the WebForms application, add a project reference to the C# MVC application.  Visual Studio will kindly let us do this because an MVC project is really just a class library project underneath all the bells and whistles.  

Build and launch your WebForms app.  It should take you to Default.aspx, which is a regular WebForms page.  Now, try navigating to the controller we created in C# by appending “/helloworld” to the URL.  If I’ve described the steps correctly, you should be greeted with something like the following:

CSharpPortableArea1

Our WebForms app is routing requests to the controller we defined in C#, and the embedded view engine is returning the corresponding view.  Do note, though, that our view is being rendered using our VB MVC view master page, and not the view master page from our C# Portable Area.  That’s by design: Portable Areas are designed to be plugged in and reused within an application.  In this case though, we’d actually like for our C# view to use the same WebForms master page as our existing WebForms content; we don’t want to maintain two distinct master pages.  It turns out that you can do this quite easily.

C# View, Meet VB WebForms Master Page

Examining our view again, we see that it provides content for two placeholders: TitleContent and MainContent.  These placeholders match the standard MVC view master page that we added to our WebForms project under ‘~/Views/Shared/Site.Master’.  If you open up the WebForms master at ‘~/Site.master’ though, you’ll notice that it defines only HeadContent and MainContent.  Let’s add a TitleContent placeholder so that our views can still define their own page titles in the usual MVC way:

<head runat="server">
    <title><asp:ContentPlaceHolder ID="TitleContent" runat="server"/></title>
    <link href="~/Styles/Site.css" rel="stylesheet" type="text/css" />
    <asp:ContentPlaceHolder ID="HeadContent" runat="server">
    </asp:ContentPlaceHolder>
</head>

Next, go back our view in the Portable Area, and change its MasterPageFile property to ‘~/Site.master’.  If you are using Resharper, you’ll notice errors indicating that there’s no master page file at that location and that your content placeholder IDs are no longer valid.  That’s because as far as Resharper (and Visual Studio) know, you are now referencing a master that doesn’t exist.  The only view master page in the C# project is at ‘~/Views/Shared/Site.master’.  All we need to do is move the master from it’s current location to the root of our C# project, and the errors will go away.  When we create new views in the future, we can reference the view master page at its new location, and our views will be generated with the correct path for our WebForms master.

Rebuild and refresh your application, and you’ll see that the Index view from our HelloWorld controller is now being rendered within the WebForms master, title-and-all:

CSharpPortableArea2

Keep in mind that what I’ve described is a proof-of-concept only; I have not tried applying this to a real project yet, and there are likely to be issues with this approach.  If you do run into issues, I’d like to hear about them.  If you want to checkout my code, you may download the sample project here.

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