i would like to upload a video and play it in thewebpage using asp.net

Ok, this is a big topic.  You can use either Silverlight or Flash (there are actually more options, but these 2 are pretty popular).

Here's an article on doing it with Silverlight:

http://www.wrox.com/WileyCDA/Section/Building-Silverlight-Video-Applications.id-306542.html

And here is one using Flash:

http://forums.asp.net/t/1170655.aspx

Walk through silver light as its safe and more compatible.

if you want your application accross different browsers use flash (*.flv)

convert your video to flv format

upload

embedd flash player in browser

these three are common procedures , there starts .... HTTP video streaming <> buffering (effective video streaming /real time streaming RTS)

http streaming - just the above works

effective video streaming /real time streaming RTS - RTSP etc .... a big ocean but quite interesting............

recent technology updation is H323