ActionExecutingContext

ActionExecutingContext is a class in ASP.NET Core MVC that represents the context in which an action method is about to be executed. It is used within the action filter pipeline. This context object provides access to various properties and methods that allow filters to inspect and modify the incoming request and outgoing response before, during, and after an action method is invoked.

Key properties of ActionExecutingContext include the Controller instance, the ActionDescriptor describing the action being executed, the RouteData containing route information, the ModelState which holds validation errors, and the ActionArguments which are the parameters passed to the action method. Filters can use this context to perform tasks such as validating input, setting view data, short-circuiting the request pipeline by setting the Result property to a non-null value, or modifying action arguments.

The ActionExecutingContext is typically created and populated by the MVC framework as part of the request processing pipeline. When an action filter's OnActionExecuting method is called, an instance of ActionExecutingContext is passed to it. This allows the filter to interact with the MVC pipeline at a crucial stage before the action method's logic is executed. Understanding ActionExecutingContext is fundamental for developing custom action filters in ASP.NET Core MVC.