How to add features to an offline VHDX file with powershell

so trying add features offline image powershell seem rejected each time.  i have read http://technet.microsoft.com/en-us/library/hh831809.aspx can't right.  so here have tried do:
want add dns offline .vhdx
opened powershell admin rights , typed following cmdlets
install-windowsfeature dns -vhdx test.vhdx -restart
offline image want install dns test.vhdx.  this file located in c drive in folder named "hyper_v" 
have tried also:
install-windowsfeature dns -vhdx c:\hyper_v\test.vhdx -restart
no luck.  please advise.  i know how add features offline image via gui know via powershell.  
thank in advance

this not hyper-v question.  might want take question powershell forum - http://social.technet.microsoft.com/forums/en-us/home?forum=winserverpowershell - or scripting guys forum - http://social.technet.microsoft.com/forums/en-us/home?forum=itcg

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.:|:.:|:. tim

Windows Server  >  Setup Deployment