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Different Versions of Integrated Web Server in Visual Studio 2010

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3 Oct 2010CPOL
Different Versions of Integrated Web Server in Visual Studio 2010


While running your ASP.NET application, you might have found it to be running on Integrated Web development environment. Visual Studio 2010 comes with two versions of Integrated Web Development environment which could run side by side. In case you run your ASP.NET application in VS 2010, you can have an option to choose between the two versions of Web Development environment, one running CLR 2.0, which was there before VS2010 and a new version of Web Dev with CLR 4.0. Multi – targeting allows you to configure your Visual Studio to run more than one Web Dev server at a time, one using CLR 2.0 and another using CLR 4.0

In one of my ASP.NET Online sessions, I had talked about the multi targeting features of Visual Studio 2010 for web development. During the demo I have shown, how can we target two different versions of .NET CLR version at the same time. Some of the attendees had some doubts on that. So in this blog post, I am going to explain how we can target two different versions of CLR at the same time.

To demonstrate it, start with a new Visual Studio Instance, and create a solution file which contains two different Framework versions of web applications. Let’s say there are two web applications which are targeted to ASP.NET 3.5 and ASP.NET 4.0 version.

1 2

Below is the structure of your solution files which contains two different projects of different Framework versions.


Now, if you run these two applications individually, for .NET 3.5 (ASP3_5Apps), you will see it is targeting CLR Version 2.0.


And if you set 4.0 project as the startup project, you will see the ASP.NET 4.0 application is targeting CLR Version 4.0.


Now, we can see that individually two different applications targeting two different frameworks. Now let's have a look, if we run these two different framework applications at the same time. To set multiple projects as start up project, right click on Solution and Go To Properties and select the option for multiple startup project. You can read my blog post How to setup multiple startup projects in Visual Studio? for more details.


Click on Apply and Ok. And run the application. You will find that both applications run at the same time and both of them target two different framework versions.


Yes, they are targeting to two different frameworks at the same time. This is really helpful, for backward compatibility, like say, your services running on .NET 2.0 version and you are developing a frontend application using .NET 4.0.

If you are hosting the Visual Studio application in IIS, VS 2010 will correctly update the application pool ASP.NET version based on the selected framework from Visual Studio.

targetiis targetiisff


In this blog post, I have explained how you can use a different version of Integrated ASP.NET engine to run ASP.NET application in VS 2010 along with targeting CLR version (CLR 2 and CLR 4) at the same time. I have also explained side by side execution of different framework versions of ASP.NET application.

Hope this will help you.



Filed under: .NET 4.0, ASP.NET 4.0, Visual Studio 2010 Image 10 Image 11 Image 12 Image 13 Image 14 Image 15 Image 16 Image 17


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Abhijit Jana
Technical Lead
India India
.NET Consultant | Former Microsoft MVP - ASP.NET | CodeProject MVP, Mentor, Insiders| Technology Evangelist | Author | Speaker | Geek | Blogger | Husband

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Twitter : @AbhijitJana
My Kinect Book : Kinect for Windows SDK Programming Guide

Comments and Discussions

GeneralMy vote of 5 Pin
thatraja6-Oct-10 2:21
protectorthatraja6-Oct-10 2:21 
GeneralRe: My vote of 5 Pin
Abhijit Jana17-Oct-10 21:13
mentorAbhijit Jana17-Oct-10 21:13 
GeneralMy vote of 5 Pin
Petr Pechovic4-Oct-10 6:14
professionalPetr Pechovic4-Oct-10 6:14 
GeneralRe: My vote of 5 Pin
Abhijit Jana17-Oct-10 21:11
mentorAbhijit Jana17-Oct-10 21:11 
GeneralMy vote of 5 Pin
Kunal Chowdhury «IN»3-Oct-10 19:07
mentorKunal Chowdhury «IN»3-Oct-10 19:07 
GeneralRe: My vote of 5 Pin
Abhijit Jana17-Oct-10 21:04
mentorAbhijit Jana17-Oct-10 21:04 
GeneralMy vote of 5 Pin
Brij3-Oct-10 18:52
mentorBrij3-Oct-10 18:52 
GeneralRe: My vote of 5 Pin
Abhijit Jana3-Oct-10 19:05
mentorAbhijit Jana3-Oct-10 19:05 
GeneralMy vote of 5 Pin
Abhishek Sur3-Oct-10 10:34
professionalAbhishek Sur3-Oct-10 10:34 
GeneralRe: My vote of 5 Pin
Abhijit Jana3-Oct-10 18:22
mentorAbhijit Jana3-Oct-10 18:22 

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Posted 3 Oct 2010

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