如何在ASP中的每一个控制器操作之前获得要执行的代码。净MVC 2 ?

I want to check some things about the state of the session, the user agent, etc, and possibly take action and return a special view BEFORE a controller method gets a chance to execute. For example:

我想检查一些关于会话状态、用户代理等的事情，并且可能在控制器方法得到执行之前，采取行动并返回一个特殊的视图。例如:

Most common:
User requests Home/Index
System checks to make sure x != 0.
x does not equal zero, so the Home/Index controller executes like normal.

最常见的:用户请求Home/Index系统检查以确保x != 0。x不等于0，所以Home/Index控制器像往常一样执行。

But, sometimes:
User requests Home/Index
System checks to make sure x != 0.
x DOES equal zero. The user must be notified and the requested controller action cannot be allowed to execute.

但是，有时:用户请求Home/Index系统检查以确保x != 0。x = 0。必须通知用户并不能执行所请求的控制器操作。

I think this involves the use of ActionFilters. But I have read about them and I don't understand if I can preempt the controller method and return a view before it executes. I am sure I could execute code before the controller method runs, but how do I keep it from running in some instances and return a custom view, or direct to a different controller method?

我认为这涉及到使用actionfilter。但是我已经读过它们，我不知道是否可以抢占controller方法并在它执行之前返回一个视图。我确信我可以在controller方法运行之前执行代码，但是我如何防止它在某些实例中运行并返回自定义视图，或者直接返回到另一个控制器方法?

Update: I implemented RM's solution. This is what I did:

更新:我实现了RM的解决方案。这就是我所做的:

public class MyAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        if (myValue == wrongValue)
        {
            filterContext.Result = new ViewResult{ViewName = "Notice"};
        }
        base.OnActionExecuting(filterContext);
    }
}

Now, when myValue is wrong, those users get the Notice view and the requested controller is never executed. To make this work I applied it to a ControllerBase that all my Controllers inherit from.

现在，当myValue出错时，这些用户会得到通知视图，并且请求的控制器不会被执行。为了完成这项工作，我将它应用到我所有的控制器都继承的控制器基础上。

2 个解决方案

#1

All depends what exactly you want to do, and how. Three options below:

这一切都取决于你到底想做什么，以及如何去做。下面三个选项:

You can use route constraints for this. They are executed when evaluating the route to match to.

您可以为此使用路由约束。在评估匹配的路由时执行。

routes.MapRoute(
    "HomeWithConstraint",
    "Home/{action}",
    new {controller="Home", action="index"},
    new { x = new MyCustomRouteConstraint () }
);

// without constraint, i.e. if above didnt pass
routes.MapRoute(
    "HomeWithConstraint",
    "Home/{action}",
    new {controller="Home", action="index"}
);

The MyCustomRouteConstraint type above would check for x==0 etc in your example. Not sure exactly what you want to do, but this will allow you to check conditions before running and set additional route values etc.

上面的MyCustomRouteConstraint类型将在示例中检查x==0等等。不确定您想要做什么，但是这将允许您在运行之前检查条件并设置额外的路由值等。

See here for example of custom route constraints.

请参见这里的自定义路由约束示例。

Alternativly, yes you can use a custom ActionFilter, just apply it to the controller class, and it will be called before any action is executed. Something like:

另外，您可以使用定制的ActionFilter，将它应用到controller类中，在执行任何操作之前调用它。喜欢的东西:

public class CheckXActionFilterAttribute : ActionFilterAttribute
{

      public override void OnActionExecuting(ActionExecutingContext filterContext)
      {
           if(x == 0)
           {
               // do something
               // e.g. Set ActionParameters etc
           }
           else
           {
               // do something else
           }
      }


}

Another option is to have all you controllers (or the relevant ones) inherit from a custom controller you make, and override :

另一种方法是让所有的控制器(或相关的控制器)继承自定义的控制器，并覆盖:

OnActionExecuting

See here for details.

有关详细信息,请参阅这里。

To do the same as the filter, or routing constraints.

执行与筛选器或路由约束相同的操作。

#2

One way you can do this is to redirect to a different ActionMethod to show the view. Code example is in this discussion:

一种方法是重定向到另一个ActionMethod来显示视图。代码示例在本讨论中:

Redirecting to specified controller and action in asp.net mvc action filter

重定向到asp.net mvc操作过滤器中指定的控制器和操作

#1