This chapter covers
- The filter pipeline and how it differs from middleware
- Creating custom filters to refactor complex action methods
- Using authorization filters to protect your action methods and Razor Pages
- Short-circuiting the filter pipeline to bypass action and page handler execution
- Injecting dependencies into filters
In part 1 I covered the MVC and Razor Pages frameworks of ASP.NET Core in some detail. You learned how routing is used to select an action method or Razor Page to execute. You also saw model binding, validation, and how to generate a response by returning an IActionResult from your actions and page handlers. In this chapter I’m going to head deeper into the MVC/Razor Pages frameworks and look at the filter pipeline, sometimes called the action invocation pipeline.
MVC and Razor Pages use several built-in filters to handle cross-cutting concerns, such as authorization (controlling which users can access which action methods and pages in your application). Any application that has the concept of users will use authorization filters as a minimum, but filters are much more powerful than this single use case.