是否为每个动作实例化了ActionFilterAttribute？

Question

我想在ActionFilterAttribute中有一个仅与它所驻留的动作有关的字段，例如

    public class TimedAction : ActionFilterAttribute
    {
        long start, end;

        public override void OnActionExecuting(HttpActionContext actionContext)
        {
            start = Stopwatch.GetTimestamp();

            base.OnActionExecuting(actionContext);
        }

        public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
        {
            base.OnActionExecuted(actionExecutedContext);

            end = Stopwatch.GetTimestamp();
        }
    }

是否可以安全地假设将为每个API调用操作实例化TimedAction？

编辑：我将代码更改为此，现在看来请求是共享的（是什么？），当我尝试添加键值对时出现异常：An item with the same key has already been added.

        public override void OnActionExecuting(HttpActionContext context)
        {
            var start = Stopwatch.GetTimestamp();

            context.Request.Properties.Add(new KeyValuePair<string, object>("Stopwatch", start));

            base.OnActionExecuting(context);
        }

        public override void OnActionExecuted(HttpActionExecutedContext context)
        {
            base.OnActionExecuted(context);

            var end = Stopwatch.GetTimestamp();

            object o;
            long start = 0;
            if (context.Request.Properties.TryGetValue("Stopwatch", out o))
            {
                start = (long)o;
            }
        }

Answer 1

请勿这样做，因为属性是静态定义的。您需要将其存储在请求中，例如HttpContext.Current.Items["SomeKey"]：

public override void OnActionExecuting(HttpActionContext actionContext)
{
    HttpContext.Current.Items["Now"] = DateTime.UtcNow;

    base.OnActionExecuting(actionContext);
}

public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
{
    var beginning = (DateTime) HttpContext.Current.Items["Now"];

    var end = DateTime.UtcNow;

    var interval = end - beginning;

    base.OnActionExecuted(actionExecutedContext);
}

Answer 2

显然，我所做的（参见OP中的代码）与@RicardoPeres的方法没有区别。

问题是我不小心将属性两次设置为方法。

但是我觉得里卡多的版本比我的更好，所以我保留了它。