Visual Studio 2012: Unable to attach the process. A debugger is already attached

asp.net debugging visual-studio-2012 iis w3wp
mtkachenko picture mtkachenko · Jul 7, 2014 · Viewed 22.6k times · Source

I built solution, created application in IIS and mapped it to the application folder. It works fine. Then I go to "Attach to Process", there are two w3wp.exe processes in list, but for one of them I get error "Unable to attach the process. A debugger is already attach." I've googled it but I can't find solution for my problem.

Answer

mtkachenko picture mtkachenko · Jul 7, 2014

I have installed Debug Diagnostic Tool v2.0 and as a result I have Debug Diagnostic Service which is started automatically and attached to one of w3wp processes. After turning off and disabling this service all works fine. So the general rule: if you get such error check processes in task manager which can capture your w3wp process.

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