F1 help from visual studio isolated shell 2015

I have VS2008 isolated shell based application working fine with context help enabled for F1.

I am porting it to VS2015 isolated shell.

In VS 2008 I was using 

helpService = (MsVsHelp80.Help2)serviceProvider.GetService(typeof(Microsoft.VisualStudio.VSHelp.SVsHelp));
 helpService.DisplayTopicFromKeyword(helptext);

This works just fine in Vs2008.

In VS2015 I get  "ShowHelp() exception occured with message: The method or operation is not implemented. " 

F1 key is correctly captured in vs2015 and I can break into my code and I get error on DisplaytopicFromkeyword (...)

Why it does not open the help viewer ? Is there any example code ?

Any help is appreciated.

Thanks,

AG