In ASP.NET, the Global.asax event Session_End occurs when a user session ends because it times out or is explicitly abandoned. Is this description correct or incorrect?

Introduction / Context:
Session_End is another important event in the ASP.NET Global.asax file that complements Session_Start. It provides an opportunity to perform cleanup for per user session data when the session ends. Understanding when Session_End fires, and the limitations of the event, is important for building robust session based applications and for answering life cycle questions in interviews.

Given Data / Assumptions:

• We are using ASP.NET session state, typically in the InProc mode.
• The Global.asax file defines a Session_End handler.
• The statement claims that Session_End occurs when users stop requesting pages and the session times out, or when the session is explicitly ended.

Concept / Approach:
Session_End is raised by ASP.NET when a session is removed from memory in certain modes. This usually happens when the session timeout period expires without activity or when code calls Session.Abandon. The event allows you to log or clean up session specific data. However, it is important to remember that Session_End only works reliably in InProc session mode; when you use out of process modes such as StateServer or SQLServer, Session_End does not fire because session state is managed outside the ASP.NET process.

Step-by-Step Solution:
Step 1: When a user interacts with the application, ASP.NET maintains a session using a session identifier stored in a cookie or URL, and an associated data store. Step 2: The application may update the session on each request, resetting its timeout counter. Step 3: If the user stops making requests and the configured timeout interval passes, the session is considered expired. Step 4: In InProc mode, when ASP.NET removes that session from memory, it raises the Session_End event in Global.asax, or it may raise Session_End when Session.Abandon is called explicitly in code. Step 5: Inside Session_End, you can perform per session cleanup such as logging or releasing resources, understanding that this may not run for sessions stored out of process.

Verification / Alternative check:
You can test Session_End by setting a short session timeout in web.config and logging messages in the Session_End handler. After a period of inactivity longer than the timeout, the log should show that the event fired. If you switch to out of process session modes and repeat the test, you will typically see that Session_End does not fire, which confirms that the event is tied to internal session management in the ASP.NET worker process.

Why Other Options Are Wrong:
Option B is wrong because Session_End does not fire on every request; it fires only when a session ends. Option C is incorrect because operating system shutdown is not the direct trigger for this event, although shutting down IIS may cause many sessions to end without individual Session_End events. Option D is clearly wrong because Session_End is an ASP.NET event, not a database trigger in SQL Server.

Common Pitfalls:
A major pitfall is relying on Session_End to perform critical work such as persisting important data, especially when using out of process session modes where the event does not fire. Another issue is assuming that Session_End always runs immediately at the timeout moment, when in reality garbage collection and memory management can affect the exact timing. Good application design considers Session_End as a convenience for cleanup rather than the only place to perform essential persistence logic.

Final Answer:
The description is correct for InProc session mode, because Session_End fires when a user session ends due to timeout or explicit abandonment, allowing session specific cleanup.