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How to run ASP.NET 2.0 and ASP.NET 1.1 side-by-side

(Kristofer Gafvert, April 8, 2006)


This article will explain how to install and run ASP.NET 2.0 and ASP.NET 1.1 side-by-side on IIS 6.0. ASP.NET 2.0 is backward compatible and makes it possible to run ASP.NET 1.1 applications on a server with only ASP.NET 2.0 installed. Most web applications developed for ASP.NET 1.1 will not experience any problems using the newer ASP.NET 2.0 framework. But in certain situations, the web application needs to be modified so that it will run as expected. In this situation, running ASP.NET 2.0 and ASP.NET 1.1 side-by-side is an option during the migration of the web application.

Installation and configuration

You cannot run different versions of the .NET Framework in the same process, so on IIS 6.0 you must run them in separate application pools. If you do run them in the same application pool, the following message will be logged in the Application event log:

It is not possible to run different versions of ASP.NET in the same IIS process. Please use the IIS Administration Tool to reconfigure your server to run the application in a separate process.

  • In IIS Manager, right click "Application Pools" and select New->Application Pool
  • Type a name for the new application pool, and select whether to use default settings or an existing application pool as a template
New application pool

To select which application pool and ASP.NET version to use:

  • In IIS Manager, right click the website (or some other application root) and select "Properties"
  • On the "Home Directory" (or "Directory") tab, select the application pool to be used and click "Apply"
  • On the ASP.NET (this tab will be added when you install .NET Framework 2.0), select the ASP.NET version and click "Apply"
Select ASP.NET version in IIS Manager

It is also possible to use aspnet_regiis.exe to update the script maps (select which ASP.NET version to use). This is the preferred way if multiple applications must be changed to use either of the versions because it is scriptable. The -s option can be used to set up the script maps for a specific application, for example:

aspnet_regiis.exe -s W3SVC/1/ROOT/MyApplication

Since each version of .NET Framework comes with its own version of this file, it is important to use the file for the version of ASP.NET you want to set up.


Configuring an ASP.NET Application for an ASP.NET Version
ASP.NET 2.0 Hosting Deployment Guide