How to disable Session State
For those pages that do not, you can indicate that session state is not needed and prevent session data from being fetched from the store in requests to these pages.
For pages that do not update session state, you can indicate that read-only access is required.
<%@ Page EnableSessionState="False" %>
or <%@ Page EnableSessionState="ReadOnly" %>
You can do it on a application wide way by changing web config as well
<!--No session state by default-->
<configuration>
<system.web>
<pages enableSessionState="false" />
</system.web>
</configuration>
<!--Read-only session state by default-->
<configuration>
<system.web>
<pages enableSessionState="ReadOnly" />
</system.web>
</configuration>