W2wp.exe has a debugger attached, but the debugger is not configured to debug this unhandled exception

First, the problem description

Yesterday, the system was linked, using the VS2010 attachment process, the W2wp.exe process is added to the VS2010 debugging process, so that other systems access our system, you can capture breakpoints for debugging

However, today F5 debugging, found that the direct error "W2wp.exe has a debugger attached, but the debugger is not configured to debug this unhandled exception." To debug this exception, you must detach the current debugger "

Second, the problem analysis:

W2wp.exe: is a process that is associated with an application pool in IIS (Internet Information Server), and if you have multiple application pools, there will be multiple W3wp.exe process instances running. This process is used to allocate a large amount of system resources.

Third, problem solving

Internet Information Services (IIS) Manager → find deployment site → Delete, republish

Although the problem has been solved, but I still do not understand why, I hope to understand the recovery

W2wp.exe has a debugger attached, but the debugger is not configured to debug this unhandled exception