Question

In Visual Studio 2010,
I want to debug two web applications running on IIS at the same time.
When debugging the first application it is ok. But when starting to debug the second application and first program is still in debug mode, Visual Studio prompts:

unable to start debugging on the web server. a debugger is already
attached

How can I solve this problem?

Answer 1

To summarize, one has to set different application pools in IIS for the two applications to debug.

Here is a rough instruction, given that both applications have been deployed to IIS once within Visual Studio.

1. Open the Internet Information Services (IIS) Manager
2. Click Application Pools on the left pane
3. On the right pane add another integrated application pool, let’s name it Second ASP.NET 4.0 Integrated
4. For one application, open the Advanced Settings…
5. In the properties view finally select Second ASP.NET 4.0 Integrated as the application pool

This way the applications should be debuggable in parallel because each Application Pool spawns a new operating system process to which a separate debugger can be attached.