ASP.NET MVC ActionFilterAttribute的执行顺序

ASP.NET MVC里面我们要自定义ActionFilter的时候会发现有4个方法可以override：OnActionExecuting，OnActionExecuted，OnResultExecuting，OnResultExecuted。他们分别在什么时候执行一直是困扰人类的一个问题。我代表人类做了一个简单的实验：

首先自定义一个ActionFilter，每个方法执行的时候都在VS的OUTPUT窗口输出信息：

public class TestActionFilter : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        Debug.WriteLine("OnActionExecuting");
        base.OnActionExecuting(filterContext);
    }

    public override void OnActionExecuted(ActionExecutedContext filterContext)
    {
        Debug.WriteLine("OnActionExecuted");
        base.OnActionExecuted(filterContext);
    }

    public override void OnResultExecuting(ResultExecutingContext filterContext)
    {
        Debug.WriteLine("OnResultExecuting");
        base.OnResultExecuting(filterContext);
    }

    public override void OnResultExecuted(ResultExecutedContext filterContext)
    {
        Debug.WriteLine("OnResultExecuted");
        base.OnResultExecuted(filterContext);
    }
}

Controller里为了搞清执行顺序，也需要输出：

[TestActionFilter]
public ActionResult Index()
{
    Debug.WriteLine("Before return View()");
    return View();
}

最后是View：

@{
    Debug.WriteLine("Hello from Index.cshtml");
}

执行结果是这样的，有图有JJ：

1. OnActionExecuting

2. Before return View()

3. OnActionExecuted

4. OnResultExecuting

5. Hello from Index.cshtml

6. OnResultExecuted