dear mostafadotnet
there is no problem using WDM TV tuner cars via c# or other managed languages
but as i created my own fully completed commercial software and i'm using it.
so i have some...

let me know what your problem exactly is.
as i got.you are implementing a directx 9.0 application via c# to play tv from your capture card
if i know what exactly your problem is may be i can help...

may be this will be useful

http://www.codeproject.com/cs/media/tvfinetune.asp