ASP. net mvc transmits the environment parameters required for the execution process by encapsulating context objects.
Public class ControllerContext
{
Public virtual ControllerBase Controller {get; set ;}
Public virtual HttpContextBase HttpContext {get; set ;}
Public RequestContext {get; set ;}
Public virtual RouteData {get; set ;}
}
As the initial state and base class of the context, ControllerContext contains basic request information. AuthorizationContext, predictioncontext, and ViewContext have simple logic and do not need to spend more ink. What we really need to know is the impact of the Executing/Executed context on the execution process.
To make it easier to observe the results, we write test code to assist our analysis.
[AttributeUsage (AttributeTargets. Class | AttributeTargets. Method, AllowMultiple = true)]
Class MyActionFilterAttribute: ActionFilterAttribute
{
Public string Name {get; set ;}
Private void Print ()
{
Var method = new StackFrame (1). GetMethod ();
HttpContext. Current. Response. Write (String. Format ("{0}. {1} <br/>", this. Name, method. Name ));
}
Public override void OnActionExecuting (ActionExecutingContext filterContext)
{
Print ();
}
Public override void OnActionExecuted (ActionExecutedContext filterContext)
{
Print ();
}
Public override void OnResultExecuting (ResultExecutingContext filterContext)
{
Print ();
}
Public override void OnResultExecuted (ResultExecutedContext filterContext)
{
Print ();
}
}
Public class TestController: Controller
{
[MyActionFilter (Name = "Filter1", Order = 1)]
[MyActionFilter (Name = "Filter2", Order = 2)]
[MyActionFilter (Name = "Filter3", Order = 3)]
Public ActionResult Index ()
{
Response. Write ("Action Method! <Br/> ");
Return Content ("View Render! <Br/> ");
}
}
By the way, let's take a look at the execution results.
Filter1.OnActionExecuting
Filter2.OnActionExecuting
Filter3.OnActionExecuting
Action Method!
Filter3.OnActionExecuted
Filter2.OnActionExecuted
Filter1.OnActionExecuted
Filter1.OnResultExecuting
Filter2.OnResultExecuting
Filter3.OnResultExecuting
View Render!
Filter3.OnResultExecuted
Filter2.OnResultExecuted
Filter1.OnResultExecuted
1. ActionExecutingContext
In ActionExecutingContext, The Result attribute is the only one that may generate a ".
Public class ActionExecutingContext: ControllerContext
{
Public virtual ActionDescriptor {get; set ;}
Public virtual IDictionary <string, object> ActionParameters {get; set ;}
Public ActionResult Result {get; set ;}
}
Normally, the returned results of the Action Method are stored. However, check ControllerActionInvoker. InvokeActionMethodFilter ().
Internal static ActionExecutedContext InvokeActionMethodFilter (filter, preContext, continuation)
{
Filter. OnActionExecuting (preContext );
If (preContext. Result! = Null)
{
Return new ActionExecutedContext (preContext, preContext. ActionDescriptor,
True/* canceled */, null/* exception */)
{
Result = preContext. Result
};
}
...
}
If preContext. Result! = Null, the method is terminated. We know that this Method is nested and executed. That is to say, once preContext. Result is assigned a non-null value, subsequent filters will not be executed, including Action Method. Try it.
Class MyActionFilterAttribute: ActionFilterAttribute
{
...
Public override void OnActionExecuting (ActionExecutingContext filterContext)
{
Print ();
If (Name = "Filter2") filterContext. Result = new EmptyResult ();
}
...
}
Output:
Filter1.OnActionExecuting
Filter2.OnActionExecuting
Filter1.OnActionExecuted
Filter1.OnResultExecuting
Filter2.OnResultExecuting
Filter3.OnResultExecuting
Filter3.OnResultExecuted
Filter2.OnResultExecuted
Filter1.OnResultExecuted
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