Custom Action Method Selector in MVC
Custom Action Method Selector in MVC
http://www.codeproject.com/Articles/291433/Custom-Action-Method-Selector-in-MVC
Introduction
The default routing algorithm for how the ASP.NET MVC framework invokes actions is like {controller}/ {action}/ {id} patterns.
But this becomes more complex when you have two methods with the same name, or when you invoke an action when form data is submitted, or execute a method only when an AJAX request is made.
Implementation
This can be done using ActionMethodSelector attributes. We generally use method selectors like:
AcceptVerbs ActionNameAcceptVerbs
This attribute is used when we want to execute some action when a particular HTTP operation is performed like POST, GET, DELETE, etc. E.g.:
Collapse | Copy Code
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Create(Employee employee)
{
// To Do Code Here
}
The above method is executed when an HTTP POST operation is performed.
AcceptName
This attribute is used when you expose an action name with a different name than its method name, or you can use an action name attribute to expose two methods with the same name as the action with different names. E.g.:
Collapse | Copy Code
[ActionName(“Edit”)]
[AcceptVerbs(HttpVerbs.Get)]
public ActionResult Edit_GET(Employee employee)
{
// To Do Code Here
}
[ActionName(“Edit”)]
[AcceptVerbs(HttpVerbs.Post)]
Public ActionResult Edit_POST(Employee employee)
{
// To Do Code Here
}
Custom Action Method Selector
You can build your own ActionMethodSelector attributes by deriving from the abstract ActionMethodSelectorAttribute class.
This is an extremely simple class; you just need to override the method named IsValidForRequest () . If this returns false, this action method is not executed.
Now take a simple example of the Custom Action Method Selector. Develop an Ajaxmethod custom attribute useful for when you want to execute some action when an AJAX request is made.
The first step is to create an MVC application. Then add a class file named AjaxMethod.cs and inherit that class from ActionMethodSelectorAttribute . Then override a method named IsValidForRequest() . Your class will look like below:
Collapse | Copy Code
public class AjaxMethod:ActionMethodSelectorAttribute
{
public override bool IsValidForRequest(ControllerContext controllerContext,
System.Reflection.MethodInfo methodInfo)
{
return controllerContext.HttpContext.Request.IsAjaxRequest();
}
}
In the IsValidForReuest method, we check the Request object for the AJAX request.
Now we can use the Ajaxmethod attribute in our controller when you want to execute some action only when an AJAX request comes. For this, add a controller named NewsController into the controller folder. In this controller, we define two index actions : first index action only executes when a page is posted back and the second action is invoked when an AJAX request comes. Your controller will look like below:
Collapse | Copy Code
public class NewsController : Controller
{
private readonly List< string > _news = new List< string >();
private Random _rnd = new Random();
public NewsController()
{
_news.Add( " Moon Explodes" );
_news.Add( " Stock Market up 200 percent" );
_news.Add( " Talking Robort Created!" );
}
// // GET: /News/
public ActionResult Index()
{
var SelectedIndex = _rnd.Next(_news.Count);
ViewData[ " News" ] = _news[SelectedIndex];
return View();
}
[AjaxMethod]
[ActionName( " Index" )]
public string Index_AJAX()
{
var SelectedIndex = _rnd.Next(_news.Count);
return _news[SelectedIndex];
}
}
Now add a View named index.aspx for displaying news and add the below markup into that:
Collapse | Copy Code
< script type =" text/javascript" src =" Scripts/MicrosoftAjax.js" > </ script >
< script type =" text/javascript" src =" Scripts/MicrosoftMvcAjax.js" > </ script >
<% = Ajax.ActionLink( " Get News" , " Index" , new AjaxOptions { UpdateTargetId = " news" }) %>
< span id =" news" % > <% :ViewData[ " News" ] %> < / span >
Now run the application. You will find that when the page loads the first time the first index action executes and when you click on the GetNews link at that time, the second index action executes. The first time, it will go check the Ajaxmethod attribute but the IsValidForRequest method will return false and then it will execute the first index action, but when you click on the link at that time, IsValidForRequest returns true and executes the second action.
Conclusion
Some of the least customized but very useful extension points in ASP.NET MVC are action method selector attributes. But using them, we can make seemingly complex things trivial.
License
This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)
作者： Leo_wl
出处： http://www.cnblogs.com/Leo_wl/
本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。
版权信息查看更多关于Custom Action Method Selector in MVC的详细内容...