IIS maintenance page with App_offline.htm

To prevent that halfway-updated websites are shown to users – it is recommendable to set up an IIS maintenance page.

Thus, the user gets reliable information instead of a faulty web application.

You can realize the maintenance note via app_offline.htm in a few steps.

Faulty web application during app update on the IIS

ASP.NET web applications hosted on an Internet-Information Server (IIS) have their own interesting features.
Any administrator or developer responsible this kind of web applications has been faced with the following task:

Single components (or even the whole application) have to be changed to implement necesaary updates.

In most cases these challenges occur:

• Files (DLLs) cannot be deleted because they are in use
• The user will see a faulty or half way-updated website
  in case he or she accesses the website during the update

Of course, there are different ways to solve this task. A rather elegant one is to display a maintenance note. Like that, the user does not have the impression to use a faulty application and can adapt to the changes. And you might aggree, that it is better to display a maintenance note than giving the user the impression of a defective website.

Configuring an IIS maintenance page with App_offline.htm

Here are 3 steps for you to set up a user-friendly IIS maintenance page for an update:

1. Create a file with the following name in the application directory:

   App_offline.htm
   

2. As soon as the file is created, the web application will be shut down and the user only sees the content of the app_offline.htm file.
    
    Create your maintenance web page and put some information about the time and extent of the maintenance work.
    
3. After the work/update has been concluded, just delete or rename the file. You don’t need to create a new file every time.
   I just rename it to app__offline.htm (e.g. with double underscore) and switch it back to app_offline.htm when I need it for the next update.

This process is supported by IIS versions for IIS 6.0 and higher.