MVC中IActionFilter过滤器俄罗斯套娃的实现方式

看mvc的源码我们知道，它是在 ControllerActionInvoker 类中执行 InvokeAction 方法来实现过滤器和action方法执行的。 

通过查看源码我们知道，他是通过调用 InvokeActionMethodWithFilters 方法来实现IActionFilter过滤器和action方法执行的，如图 

点进去这个方法我们可以看到 

1 protected virtual ActionExecutedContext InvokeActionMethodWithFilters(ControllerContext controllerContext, IList<IActionFilter> filters, ActionDescriptor actionDescriptor, IDictionary<string, object> parameters)
2 {
3     ActionExecutingContext preContext = new ActionExecutingContext(controllerContext, actionDescriptor, parameters);
4     Func<ActionExecutedContext> seed = () => new ActionExecutedContext(controllerContext, actionDescriptor, false, null)
5     {
6         Result = this.InvokeActionMethod(controllerContext, actionDescriptor, parameters)
7     };
8     return filters.Reverse<IActionFilter>().Aggregate(seed, (Func<ActionExecutedContext> next, IActionFilter filter) => () => ControllerActionInvoker.InvokeActionMethodFilter(filter, preContext, next))();
9 }

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