Can anybody help me to find a task management which has such funtionality:
Find Events/Tasks Time
Book events
Create a request to others
Cancel/Change a task time/priority
Confirm or decline a meeting/event

and also I want it to use SQL SERVER database as its databse and using c# language.

Thanks in advance.

Not exactly the same, but something close to it can be the Issuer Tracker sample project, check the link below:

http://www.asp.net/StarterKits/White...Whitepaper.htm

Regards
Mike

Don't expect too much, too soon.

Thanks Mike for you reply :)