Hi akshay806,
You can increase the session timeout in the following ways.
Web.config
Open your web.config file and under the system.web section add the following.
<sessionState timeout = "60" mode = "InProc" />
Default Session Timeout is 20 minutes. Replace 60 (minutes) with time you wish.
Global.asax file
Under the Session_Start method, set the timeout property of the session to the required value like this.
Session.Timeout = "60";