OnActionExecuted

OnActionExecuted is a method in ASP.NET MVC and ASP.NET Core that is executed after an action method has completed its execution. This method is part of the action filter pipeline and provides a hook for developers to perform actions after the controller action has run but before the result is executed. It is commonly used for tasks such as logging, authorization checks, modifying the action result, or handling exceptions.

This method receives an ActionExecutedContext object, which contains information about the action method's execution, including the result that was returned and any exceptions that may have occurred. Developers can inspect this context to determine how to proceed. For instance, if an exception has been thrown, OnActionExecuted can be used to handle it gracefully, perhaps by returning a specific error view or logging the error details. If no exception occurred, it can be used to modify the ActionExecutedContext.Result property, thereby altering the response that will be sent to the client.

OnActionExecuted is an overrideable method in custom action filter classes. By creating a class that inherits from ActionFilterAttribute and overriding the OnActionExecuted method, developers can implement custom logic that will be applied to controller actions. This allows for reusable cross-cutting concerns to be implemented without modifying individual action methods. In ASP.NET Core, the concept is similar, with the method signature slightly differing to accept an ActionExecutedContext.