如何避免重复为控制器中的每个操作发生的代码

Question

I have a controller which serves a number of pages. Each Page has the following code block:

public class SchoolController : Controller
{
    private UnitOfWork _unitOfWork = new UnitOfWork();

    public ActionResult Details()
    {
        var viewModel = new RegistryViewModel();

        School schoolBeingAccessed = _unitOfWork.SchoolRepository.GetLoggedinSchool();

        if (!schoolBeingAccessed.IsActive())
        {
            return RedirectToAction("NotActive");
        }
        if (!schoolBeingAccessed.IsExpired())
        {
            return RedirectToAction("Expired");
        }

        .....
   }

How can I best avoid duplicating this code? I can put this code into a function, but then I need to remember to call the function from every action in the controller.

Normally I would use something like Html.Action("CheckSchoolStatus") in the _Layout page, however I can't do that as I am redirecting, and you cannot redirect from a child action.

Can I call this code from the Layout page? Or should I use a base controller? How does that work if each View has it's own ViewModel?

Answer 1

You should use Action Filters .

From the documentation:

Action filters. These implement IActionFilter and wrap the action method execution. The IActionFilter interface declares two methods: OnActionExecuting and OnActionExecuted. OnActionExecuting runs before the action method. OnActionExecuted runs after the action method and can perform additional processing, such as providing extra data to the action method, inspecting the return value, or canceling execution of the action method.