The ResolveSource action determines the location of the source and sets the SourceDir property if the source has not been resolved yet.
The ResolveSource action must come after the CostInitialize action.
There are no ActionData messages.
The ResolveSource action must be called before using the SourceDir property in any expression. It must also be called before attempting to retrieve the value of the SourceDir property using MsiGetProperty. The ResolveSource action should not be executed when the source is unavailable, as it may be when uninstalling the application.