ASP.NET 1.1 and 2.0 Processes

Once you install ASP.NET 2.0 all the applications running on your machine will be mapped to the new version of .NET framework but this is not what you need if you want to run ASP.NET 1.1 applications while using ASP.NET 2.0 you can do one simple thing by opening your IIS manager ( I usually do it by typing into Run : inetmgr ) and you can right click your 1.1 application and select properties you will find one new tab added to your properties called "ASP.NET" , you can select the version you want your application to run under in this case select "1.1.4322.0". This will map your application to ASP.NET 1.1 not 2.0.

You can do one other thing by editing configuration of your web application just go and select the properties again and on the "Virtual Directory" tab, click "Configuration" button , you will get another property pages dialog box , you should select the "Mappings" tab , which is the first one, and from extenstions select the "aspx" extension and click "Edit" and make sure that you are pointing to the extension "c:\windows\microsoft.net\framework\v1.1.4322\aspnet_isapi.dll" or point to the framework version you need.

You may face on other problem when running ASP.NET 1.1 and 2.0 versions side by side, note that 2 different versions application cannot run side by side inside one process. You should aviod that otherwise you will get the famous "Server Unavailable" error message.

So we need to make the IIS able to serve 1.1 applications and 2.0 applications side by side , and make them run in different processes this can be eaisly acheived by the new isolation feature of IIS 6 which is provided under "Application Pools". the rule is simply that 2 different applications have different application pools run in completely different isolated processes.

So you should make a new application pool and assign it to your 2.0 Applications by doing the following from IIS manager :

1. Right-click the Web Sites folder and click Properties.
2. On the Service tab, clear the Run Web service in IIS 5.0 isolation mode check box.
3. Right click application pools node and add a new one call it any name you want.
4. You can now assign that application pool to the application you need from the directory tab in properties dialogbox.