Explain the purpose and operation of the OnActionExecuted method in MVC request processing.

The OnActionExecuted method in MVC is called after the controller action (action method) has been executed, but before the response is sent to the client.

Its purpose is to perform additional logic, such as:

• Logging the results of the action.
• Modifying the result (for example, changing the model or view).
• Handling exceptions or setting additional response headers.

Example of overriding in C#:

public override void OnActionExecuted(ActionExecutedContext context)
{
    // Log the execution time of the action
    var elapsed = DateTime.Now - _startTime;
    Console.WriteLine($"Action completed in {elapsed.TotalMilliseconds} ms");
    base.OnActionExecuted(context);
}

Thus, OnActionExecuted allows injecting cross-cutting logic after the action execution without modifying the controller method.