Part 1 of 3: Creating sub-projects in IIS with Web Application Projects

Part 1 of 3: Creating sub-projects in IIS with Web Application Projects

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First a quick intro, since this my first post on the team blog.  My name is Omar Khan.  I'm the group program manager for the web development tools team.  I manage the program management team that helps design the web tools inside of Visual Studio.

This post is one of a three part series that describes how to factor development of a single large ASP.NET application into multiple projects inside of Visual Studio 2005 using the Web Application Projects add-in.

Part 1 of 3: In this post, I’ll describe the basics on how to setup a sub-project structure using IIS. 

Part 2 of 3: The next post will describe intricacies with master pages, user controls, and project references when using a sub-project structure.

Part 3 of 3: The final part to the series will describe how to use the same technique but with the built-in development server in Visual Studio 2005.

Why use sub-projects?

With very large web applications, such as those that contain thousands of files, using a sub-project structure in Visual Studio provides several benefits. 

At development time, it provides a clean isolation between different parts of the application.  This enables different developers to own their own projects within a single web application, and allows them to make changes without affecting code that is in a different project.

As well, using sub-projects provides a clean way to compartmentalize functionality so different parts of the application can be developed in isolation from others.  The compartmentalization also enables the ability to deploy the various sub-projects to production independently from each other thus providing more flexibility around incremental updates to one part of the application without affecting other parts. 

Setting up the root project using IIS

The first thing I want to show is a step-by-step on how to setup a sub-project project structure based on developing on IIS. 

Setting up a sub-project structure in Visual Studio 2005 is fairly straightforward.  If one has done it in Visual Studio 2003, the process described below should be very familiar. 

Here is a step-by-step walkthrough of how to setup sub-projects using Visual Studio 2005 and the Web Application Projects add-in.

1)    Download and install “Web Application Projects” add-in.  The add-in can be installed from the following location:

2)    Create the root project.  The first thing we want to do is create a new Web Application project that will represent the root of the application in IIS.  To do this select File > New Project.  Choose the ASP.NET Web Application item, and type in a name and location for the root project.  In this example we’ll call the root project MyLargeWebApp.  Make sure the “Create directory for solution” checkbox is unchecked.  One can create the “Root” project in a folder in the “inetpub/wwwroot” directory for IIS, or in any other location where you wish to create the virtual root for your app.  In this example, we’ll use a location underneath “inetpub/wwwroot”. 



3)    The next step is to map the MyLargeWebApp project in IIS using the “Web” tab in project properties.  To do this, right-click on the root node of the project and select “Properties”.  Click the “Web” tab on the page that is launched, and select the “Use IIS Web Server” option.


4)    Next you need to create a virtual directory mapping in IIS to point to the location where your root project exists.  To do this click the “Create Virtual Directory” button on the same Properties page.


5)    You can now test your root project, by adding some content to default.aspx and selecting F5.  This should run launch IE and the default.aspx page will get served from IIS.


Creating sub-projects under a root project

Once the root project is up and running fine, the next step is to create a sub-project and set it up so it builds and runs as part of the same ASP.NET application represented by the root project.  The following steps describe how to do this:

1)    The first thing you need to do is add a new Web Application project to the same solution.  Make sure the MyLargeWebApp solution/project is already open in the solution explorer.  To add a new project to the solution, select “File > Add > New Project”.  Select “ASP.NET Web Application” as the template.  Then type in a name for the sub-project (“SubProject1” in this example), and set it to the location of the folder where the root project is (c:\inetpub\wwwroot\MyLargeWebApp in this example).




2)    You should now have two projects in your solution which represent a single ASP.NET application.  To verify this, go to the IIS management console by selecting Start > Run > inetmgr in Windows.  In the management console, you should see a “SubProject1” folder under single IIS web application called “MyLargeWebApp”.



3)    To get the sub project building and running a few more steps are required in Visual Studio.  The first thing you should do is delete the web.config file in the sub-project.


4)    Next you need to adjust a few of the properties for the sub-project.  Right click on the sub-project’s node in solution explorer and select “Properties”.  Under the “Compile” page change the “Build output path” to “..\bin\”.




5)    Finally in the sub-project’s properties, under the “Web” page, select the “Use IIS Web Server” option and change the “Project URL” setting to “http://localhost/MyLargeWebApp/SubProject1”.  Also check the "Overwrite application root URL" and provide the URL to the root project, which in this case is "http://localhost/MyLargeWebApp/".  Do not click the “Create Virtual Directory” button in the sub-project’s setting as you don’t want to create another application root in IIS at the sub-projects folder.


6)    Once you’ve updated these properties for the sub-project, the sub-project should be ready to go.  Add some content to the default.aspx page in the sub-project and press F5.  This should build the sub-project, deploy its DLL to the \bin of the root project, and then run the page from the sub-project.  If you select the root-project and “Show All Files” in the solution explorer, you will see in its \bin folder that there are two deployed assemblies, one for the root project (MyLargeWebApp.dll) and one for the sub-project (SubProject1.dll).




This wraps up my first post on sub-projects.  Hopefully it provides a quick introduction on how to setup a sub-project structure using the Web Application Project add-in for Visual Studio 2005. 

As mentioned in the beginning of the post, sub-projects are a good way to partition a single large ASP.NET application into several Visual Studio projects so you get the benefits of isolated development and deployment.

Looking forward to hear from you about this post, and I'll update with Part 2 hopefully next week.


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  • Hello Polo,

    In my next part which I plan to post shortly, I'll show how to use an ASCX in the root project from a sub-project.  There is a limitation on design view not displaying it fully, however at run-time it should work fine.

  • In VS 2003, I remember that I didn't need to create a seperate WAP. I just made a sub folder and createed .aspx pages in that. When compiling the project, the sub pages were compiled into the root bin.

    So, with VS 2005, I have to make a new WAP project within the existing one?

    One other way is to make two seperate WAP and copy the .dll's into the applicable "bin" folders of the virtual folders in IIS (one being a sub folder).
  • Thanks for the information.  it has answered a lot of questions i was asking myself, regarding setting up a project with sub projects.  One thing though.  i would like to set this up on a remote server, rather than have the files reside on my local workstation.  is this possible?
  • Hello Omar,

    Does this structure works with Visual Web Developer Express?
    I look for infoormations about VWDExpress "limitations". Is it possible to have solutions (or an equivalent) like .sln in VS2003? Or it is necessary to use another version?
  • Hello Dom,

    A subproject is not required by any means.  You can still create subfolders in a WAP project and put ASPX pages in them just like VS2003.  The primary reason to do a subproject is if you want pages in a sub-folder to compile into a different assembly.
  • Hello Rich,

    WAP projects only support development on a local server.  I will be adding a post soon about how to do sub-project using the built-in ASP.NET develpoment server.  That might be a usable option for you if you are unable to put IIS on your local machine.
  • Hi Michel,

    The WAP project option only works with Visual Studio Std and higher.  You can however use the default "Website" option in VWD Express which gives the core functionality needed to develop ASP.NET apps.  As well, VWD Express does support solutions, in that you can have mutliple "Websites" in a solution.

  • How would you use this sub-project architecture in conjunction with WDP?  Would you attach the web deployment project to the Root Project alone or would you attach 2 wdp's to the root and sub-project each?  What are the consequences/side effects of using WDP with this architecture?

    Also, where are the next two parts?  :)
  • Hello Mr.Khan,

    I recently saw your post and found it great for starters. I am also a starter and I am working in a similar application. But my approach has been a little different. Instead of creating a web application as a project  I have created a blank solution. And added to it other web application projects as and when required.

    Is the approach right? If not,then what is wrong with it?

    If you can , could you answerme at
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  • Thanks for this post, it will be very useful. One question though, what happens with the "Themes" if we delete the web.config file. I thought that the line "<pages theme = "MyThemeName" />" was important in the "<system.web>" section in order to have my web application compiled with my theme definitions. Is there a way to link to another web.config file? ... or am I just missing something since the beginning?
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