As noted by Aaron Stebner, there is now a registry key you can search for to detect if the Visual C++ 2010 redistributable package is installed a machine, when installing your application.
There are 3 different (but very similar) registry keys for each of the 3 platform packages. Each key has a DWORD value called “Installed” with . . . → Read More: HOW TO: Detect if the Visual C++ 2010 redistributable package is installed with WiX
Determine the name of the custom action you want to debug
Ensure you have the source code and debug symbols for your custom action
Set the MsiBreak environment variable (user or system) to the name of the custom action. For example:
Setx MsiBreak MyCustomActionName
Run your installer
At the point where your custom action is about to run, you should get . . . → Read More: HOW TO: Debug a Windows Installer custom action