WebApplicationExtension element (Iis extension)
Extension for WebApplication
CheckPath (wxs:YesNoTypeUnion) :
Executable (String, required) : Usually a Property that resolves to short file name path.
Extension (String) : Extension being registered. Do not prefix with a '.' (e.g. you should use "html", not ".html"). To register for all extensions, use Extension="*". To register a wildcard application map (which handles all requests, even those for directories or files with no extension) omit the Extension attribute completely.
Script (wxs:YesNoTypeUnion) :
Verbs (String) :