Asp.net MVC (6)

Action and filter

In Asp.net MVC, filter can only be restricted to action and controller. It inherits from actionfilterattribute and can overwrite the following important methods.
1: void onactionexecuting (actionexecutingcontext): action before execution

2: void onactionexecuted (actionexecutedcontext): The operation after the action is executed.

3: void onresultexecuting (resultexecutingcontext): executed before parsing actionresult

4: void onresultexecuted (resultexecutedcontext): After parsing the actionresult, execute

A common filter provided by the system:
1: acceptverbs
2: actionname, both of which have restrictions on Action access conditions;
3: outputcache: Set the cache;
4: validateinput, added data verification.

Example:
1: The message book list data can be written in this way, or [acceptverbs (httpverbs. Get)] can be omitted. It is the default value. This type of access is in the form of a link.

[Acceptverbs (httpverbs. Get)]
Public Actionresult index ()
{
VaR Models = Inter. findallinfo ();
Return View ( " Index " , Models );
}

2: when creating a message: we use httpverbs. Post. In this case, the corresponding action must be executed only after the form is submitted.

[Acceptverbs (httpverbs. Post)]
Public Actionresult create (guestbookinfo Model)
{
Try
{
Inter. Add (model );
VaR Models = Inter. findallinfo ();
Tempdata [ " Tempdata " ] =   " Created successfully " ;
Return Redirecttoaction ( " Index " );
}
Catch (Exception ex)
{
Modelstate. addmodelerror ( " Ex " , Ex );
Return View (model );

}
}

3: The actionnameattribute usage is similar to the acceptverbsattribute method. If no actionname is specified, the system will find the view with the same name and method name by default.

[Actionname ( " Edit " )]
Public Actionresult edit ( Int ID)

Custom filter:
Create a noclientcacheattribute without client cache. You must inherit actionfilterattribute and override the onactionexecuting method.

Public   Class Noclientcacheattribute: actionfilterattribute
{
Public   Override   Void Onactionexecuting (actionexecutingcontext filtercontext)
{
Httpcontext. Current. response. cachecontrol =   " No-Cache " ;
}

}

It is especially simple to use in action, just as it is in C.

[Noclientcache]
Public Actionresult details ( Int ID)

Acceptverbs working mechanism.

1. acceptverbsattribute class. It inherits actionmethodselectorattribute, and the important method is to override the isvalidforrequest method of the base class, which is also a filter function.

[Attributeusage (attributetargets. method, allowmultiple = False , Inherited = True )]
Public   Sealed   Class Acceptverbsattritor: actionmethodselectorattribute
{
// Fields
[Compilergenerated]
Private Icollection < String >   < Verbs > K _ backingfield;

// Methods
Public Acceptverbsattribute (httpverbs verbs );
Public Acceptverbsattribute ( Params   String [] Verbs );
Private   Static   Void Addentrytolist (httpverbs verbs, httpverbs match, list < String > Verblist, String  

entrytext);
internal static string [] enumtoarray (httpverbs verbs);
Public override bool isvalidforrequest (controllercontext, methodinfo);

//Properties
PublicIcollection<String>Verbs {[compilergenerated]Get;Private[Compilergenerated]Set;}
}

Second: isvalidforrequest method:

Public   Override   Bool Isvalidforrequest (controllercontext, methodinfo)
{
If (Controllercontext =   Null )
{
Throw   New Argumentnullexception ( " Controllercontext " );
}
String Httpmethod = Controllercontext. httpcontext. Request. httpmethod;
Return   This . Verbs. Contains < String > (Httpmethod, stringcomparer. ordinalignorecase );
}

We can see that this. verbs is a set of request. httpmethod in this method. How is it initialized? Let's look at the constructor of acceptverbsattribute. It also calls another constructor public acceptverbsattribute (Params string [] verbs)

Public Acceptverbsattribute (httpverbs verbs ): This (Enumtoarray (verbs ))
{
}

The following enumtoarray method and addentrytolist method are important. The enumtoarray method is used to collect all request. httpmethod. The addentrytolist method is used to compare the current access type with all request. httpmethod and obtain their intersection.

Internal   Static   String [] Enumtoarray (httpverbs verbs)
{
List < String > Verblist =   New List < String > ();
Addentrytolist (verbs, httpverbs. Get, verblist, " Get " );
Addentrytolist (verbs, httpverbs. Post, verblist, " Post " );
Addentrytolist (verbs, httpverbs. Put, verblist, " Put " );
Addentrytolist (verbs, httpverbs. Delete, verblist, " Delete " );
Addentrytolist (verbs, httpverbs. Head, verblist, " Head " );
Return Verblist. toarray ();
}

 

 

Private   Static   Void Addentrytolist (httpverbs verbs, httpverbs match, list < String > Verblist, String Entrytext)
{
If (Verbs & Match) ! =   0 )
{
Verblist. Add (entrytext );
}
}

Looking back at the isvalidforrequest method, it is easy to understand why this filer can be used for filtering.

Summary:Using the filter feature, we can write some extended content, such as compressing the page's attivity, and non-cached attivity.
Note: Reference: http://www.rainsts.net/article.asp? Id = 786