In ASP.NET, the Global.asax event Session_Start occurs every time a new session is created for a user visiting the application. Is this description correct or incorrect?

Introduction / Context:
ASP.NET applications often rely on session state to store per user data across multiple requests. The Global.asax file exposes events related to the application and session life cycle. Session_Start is one of these events, and understanding when it fires is important for initialising per user data correctly. Interviewers use this question to check your knowledge of basic ASP.NET life cycle events.

Given Data / Assumptions:

• We are working with an ASP.NET application that uses in process session state.
• The Global.asax file defines handlers for events including Session_Start.
• The statement claims that Session_Start occurs every time a new user visits and a new session is created.

Concept / Approach:
Session_Start is raised by ASP.NET when a new session is created for a client. This usually happens when a user first requests a page in the application and session state is enabled, or when a previous session has expired and a new one is created. The event is not raised for every request; it is tied to the creation of the session object, not mere page views. Inside Session_Start, developers often initialise session variables, counters, or lightweight per user resources.

Step-by-Step Solution:
Step 1: When a user sends the first request to an ASP.NET application that uses session state, the framework checks whether an existing session identifier is present and valid. Step 2: If no valid session exists, ASP.NET creates a new session object, assigns a new session identifier, and hooks it to the current request. Step 3: As part of this process, the Session_Start event in Global.asax is raised, allowing application code to run initialisation logic for that user. Step 4: On subsequent requests from the same user, as long as the session has not expired or been abandoned, the existing session is reused and Session_Start does not fire again. Step 5: If the session times out or is explicitly abandoned and the user later returns, a new session is created and Session_Start is raised again for that new session.

Verification / Alternative check:
You can verify this behaviour by adding logging statements inside Session_Start and watching when they appear. Only the first request that creates a new session, or a request after timeout that causes a new session, triggers the log entry. Regular postbacks and page requests from an active session do not cause Session_Start to run again. Documentation for ASP.NET life cycle events confirms that Session_Start is associated with session creation, not with every individual request.

Why Other Options Are Wrong:
Option B is wrong because Session_Start does not fire on every request; that would defeat its purpose as a session initialisation event. Option C is incorrect because Session_Start is a standard ASP.NET event that does fire when sessions are created. Option D is clearly wrong because SQL Server has no concept of a Global.asax session event; this event belongs to ASP.NET.

Common Pitfalls:
Developers sometimes place heavy logic or long running operations inside Session_Start, which can slow down the first request for each user. Another pitfall is assuming Session_Start will run for every postback, which can lead to unexpected behaviour if initialisation code is incorrectly written to depend on that. It is also important to remember that Session_Start does not fire when using certain out of process session modes in specific configurations. Keeping these details in mind helps you design reliable session initialisation logic.

Final Answer:
The description is correct, because Session_Start fires whenever ASP.NET creates a new user session for the application, such as when a new user arrives or a previous session has expired.