If you are installing .NET 4 on IIS 6 Windows Server 2003, you may be wondering if you will need to restart your server. Bottom line is YES, you will be asked to restart after the installation finishes.
I tried finding a simple answer like this before starting my own installation, but I wasn’t able to find anything clear online. I admit I may not have looked enough, but for future reference I wanted to document my findings so that someone may benefit from my experience, or just so that I will remember the answer myself.
The warning that pops up after you install .NET says you can continue without a restart, but that .NET may become unstable. I tested running a server like this without an immediate restart for a while and there was no problem with the .NET engine for any of the sites running on the server, but I suggest to anyone doing this to eventually do a restart just to be safe.
The .NET 4.0 Installer
To give some more details, you can download the ASP.NET 4.0 installer from Microsoft here:
http://www.microsoft.com/en-ca/download/details.aspx?id=17851
The Windows Imaging Component
Before you can begin installing .NET 4.0, you will be asked to download and install a Windows Imaging Component (WIC). You can download this here:
http://www.microsoft.com/en-ca/download/details.aspx?id=32
You will not be asked to restart your server after installing the WIC component, but you will be asked to restart after installing the .NET 4.0 component.
Setting up Your Site for the New Version of .NET
Once you have installed the .NET 4.0 component, you will need to set up IIS 6 to run your .NET 4.0 Web site. Note that if you are using the IIS UI to change the .NET version for a Web site, IIS will prompt you to restart the IIS worker process. It’s best to use the command line to change your .NET version as I explain in a related article:
** Just a note: before you go ahead and actually change the .NET version for one of your Web sites, make sure that you register and assign a new .NET 4.0 Application Pool and that .NET 4.0 exists as a Web Service Extension.
If .NET 4.0 doesn’t exist as a Web Service Extension then you can manually point to the ISAPI dll. It’s usually located in the default location:
[Your Default Drive]\Windows\Microsoft.NET\Framework\4.0.x\aspnet_isapi.dll
You then need to set up your .NET 4.0 Application Pool and don’t forget to assign it to your .NET 4.0 Web site under the IIS site’s Home Directory tab.
I hope this has been helpful to someone looking for the same answer as I did.
Justin Cooney 