There are posts all over the web lamenting how difficult it is to debug a custom PowerShell Module from within Visual Studio 2010 but I found a simple way to do it that works every time.  It was tricky to get right at first, but this works like a champ.

Here are the steps:

• Start Visual Studio
• go the the Properties window for your custom Module Project
• Select the ‘Start External Program’ radio button
• enter “C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe” as the destination.  This will start PowerShell and attach the debugger to the instance

• Go down to the “Start Options” and enter the text below in the “Command Line Agruments” box, including all of the quotes (naturally, you will have to change the paths for your project):

-noexit -command “& { import-module -name ‘C:\Path\To\Solution\Project\bin\Debug\CustomModule.dll’}”

This last step loads your custom module into the PowerShell instance that is being debugged.  From there, simply set your breakpoints in Visual Studio and then call your new PowerShell command from within the new PowerShell window.  It should stop on your breakpoint every time.

Happy Debugging!