Difference between application and virtual directory

Solution 1:

Those two are easy to get confused and people often use the terms interchangeably.

A virtual directory is just a pointer to a different location on disk. It points to a fixed path on disk that is different that its parent folder.

An application is a boundary between different folders. ASP.NET uses it to create a new AppDomain root (or application root). An application root uses a different global.asax, bin folder and the other app_[folders.].

In IIS6 and IIS7 if you create a virtual directory, it is not also an application by default. ASP.NET will put it in the same AppDomain as its parent folder.

In IIS6 you can convert a virtual directory or a regular folder into an application by right-clicking -> properties and Create.

In IIS7 the options are named different but it's the same in the background. Creating a virtual directory allows you to create a vdir that is still part of its parent's AppDomain i.e. not an application).

The "Add Application" option actually creates a virtual directory AND then marks it as an application. (you'll notice that it allows you to specify a path).

You can also right-click on an existing folder (or vdir) and Convert to Application. That's a way to create the application boundary on a existing regular or virtual folder.

Solution 2:

You can also check.. Did you know: Difference between Virtual Directory & Application in IIS 7 / 7.5

Edited: To quote the site, as the link is dead;

In IIS 7 / 7.5, you have an option to create a Virtual Directory and Applications.

What is a Virtual Directory?

Virtual Directory is a directory that is mapped to a local physical directory or a directory on a remote server. A Virtual Directory will have it's code executed in the same worker process as the parent process. The application pool of the Web Site and Virtual Directory is the same.

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What is an Application?

An Application is identical to the Virtual Directory except that you have an option to run an Application in a different application pool.

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NOTE: this is how the above screenshots looks like in applicationhost.config