无涯教程-ASP.NET MVC - 选择器 Action Selector是可以应用于Action方法的属性，用于响应

Action Selector是可以应用于Action方法的属性，用于响应请求而调用哪种Action方法，它有助于路由引擎选择正确的操作方法来处理特定请求。

在编写Action方法时，它起着至关重要的作用。这些选择器将根据操作方法来决定方法调用的行为，它通常用于为操作方法的名称加上别名。

Action Selector选择器属性有三种类型-

ActionName
NonAction
ActionVerbs

ActionName

此类表示用于操作名称的属性，它还允许开发人员使用与方法名称不同的操作名称。

让我们来看上一章中的一个简单示例，其中HomeController包含两个操作方法。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
namespace MVCFiltersDemo.Controllers {
public class HomeController : Controller{
//GET: Home
public string Index(){
return "This is ASP.Net MVC Filters Tutorial";
}
  </span><span class="kwd">public</span><span class="pln"> </span><span class="kwd">string</span><span class="pln"> </span><span class="typ">GetCurrentTime</span><span class="pun">(){</span><span class="pln">
     </span><span class="kwd">return</span><span class="pln"> </span><span class="typ">DateTime</span><span class="pun">.</span><span class="typ">Now</span><span class="pun">.</span><span class="typ">ToString</span><span class="pun">(</span><span class="str">"T"</span><span class="pun">);</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">

}
}

让我们通过在GetCurrentTime()上方写[ActionName("CurrentTime")]为GetCurrentTime应用ActionName选择器，如以下代码所示。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
namespace MVCFiltersDemo.Controllers {
public class HomeController : Controller{
//GET: Home
public string Index(){
return "This is ASP.Net MVC Filters Tutorial";
}
  </span><span class="pun">[</span><span class="typ">ActionName</span><span class="pun">(</span><span class="str">"CurrentTime"</span><span class="pun">)]</span><span class="pln">
  </span><span class="kwd">public</span><span class="pln"> </span><span class="kwd">string</span><span class="pln"> </span><span class="typ">GetCurrentTime</span><span class="pun">(){</span><span class="pln">
     </span><span class="kwd">return</span><span class="pln"> </span><span class="typ">DateTime</span><span class="pun">.</span><span class="typ">Now</span><span class="pun">.</span><span class="typ">ToString</span><span class="pun">(</span><span class="str">"T"</span><span class="pun">);</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">

}
}

现在运行此应用程序，并在浏览器 http://localhost:62833/Home/CurrentTime 中输入以下URL，您将收到以下输出。

您可以看到我们使用了CurrentTime而不是原始操作名称，即上面的URL中的GetCurrentTime。

NonAction

NonAction是另一个内置属性，它指示Controller的公共方法不是操作方法，当您不希望将某个方法视为Action方法时，可以使用该方法。

让我们看一个简单的示例，在HomeController中添加另一个方法，并使用以下代码应用NonAction属性。

using MVCFiltersDemo.ActionFilters;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
namespace MVCFiltersDemo.Controllers {
public class HomeController : Controller{
//GET: Home
public string Index(){
return "This is ASP.Net MVC Filters Tutorial";
}
  </span><span class="pun">[</span><span class="typ">ActionName</span><span class="pun">(</span><span class="str">"CurrentTime"</span><span class="pun">)]</span><span class="pln">
  </span><span class="kwd">public</span><span class="pln"> </span><span class="kwd">string</span><span class="pln"> </span><span class="typ">GetCurrentTime</span><span class="pun">(){</span><span class="pln">
     </span><span class="kwd">return</span><span class="pln"> </span><span class="typ">TimeString</span><span class="pun">();</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">
	
  </span><span class="pun">[Non</span><span class="typ">Action</span><span class="pun">]</span><span class="pln">
  </span><span class="kwd">public</span><span class="pln"> </span><span class="kwd">string</span><span class="pln"> </span><span class="typ">TimeString</span><span class="pun">(){</span><span class="pln">
     </span><span class="kwd">return</span><span class="pln"> </span><span class="str">"Time is "</span><span class="pln"> </span><span class="pun">+</span><span class="pln"> </span><span class="typ">DateTime</span><span class="pun">.</span><span class="typ">Now</span><span class="pun">.</span><span class="typ">ToString</span><span class="pun">(</span><span class="str">"T"</span><span class="pun">);</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">

}
}

新方法TimeString从GetCurrentTime()中调用，但是您不能将其用作URL中的操作。

让我们运行该应用程序，并在浏览器中指定以下URL http://localhost:62833/Home/CurrentTime 。您将收到以下输出。

现在让我们检查/TimeString 作为URL中的操作，看看会发生什么。

您会看到它显示" 404-Not Found"错误。

ActionVerbs

您可以应用的另一个选择器过滤器是ActionVerbs属性，因此，这将对特定操作的指示限制为特定的HttpVerbs，您可以定义两个具有相同名称的不同操作方法，但是一个操作方法将响应HTTP Get请求，而另一个操作方法将响应HTTP Post请求。

MVC框架支持以下ActionVerb。

HttpGet
HttpPost
HttpPut
HttpDelete
HttpOptions
HttpPatch

让我们看一个简单的示例，在该示例中我们将创建EmployeeController。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
namespace MVCControllerDemo.Controllers {
public class EmployeeController : Controller{
//GET: Employee
public ActionResult Search(string name = “No name Entered”){
var input = Server.HtmlEncode(name);
return Content(input);
}
}
}

现在，使用以下代码添加另一个具有相同名称的操作方法。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
namespace MVCControllerDemo.Controllers {
public class EmployeeController : Controller{
//GET: Employee
//public ActionResult Index()
//{
//return View();
//}
  </span><span class="kwd">public</span><span class="pln"> </span><span class="typ">ActionResult</span><span class="pln"> </span><span class="typ">Search</span><span class="pun">(</span><span class="kwd">string</span><span class="pln"> name</span><span class="pun">){</span><span class="pln">
     </span><span class="kwd">var</span><span class="pln"> input </span><span class="pun">=</span><span class="pln"> </span><span class="typ">Server</span><span class="pun">.</span><span class="typ">HtmlEncode</span><span class="pun">(</span><span class="pln">name</span><span class="pun">);</span><span class="pln">
     </span><span class="kwd">return</span><span class="pln"> </span><span class="typ">Content</span><span class="pun">(</span><span class="pln">input</span><span class="pun">);</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">
	
  </span><span class="kwd">public</span><span class="pln"> </span><span class="typ">ActionResult</span><span class="pln"> </span><span class="typ">Search</span><span class="pun">(){</span><span class="pln">
     </span><span class="kwd">var</span><span class="pln"> input </span><span class="pun">=</span><span class="pln"> </span><span class="str">"Another Search action"</span><span class="pun">;</span><span class="pln">
     </span><span class="kwd">return</span><span class="pln"> </span><span class="typ">Content</span><span class="pun">(</span><span class="pln">input</span><span class="pun">);</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">

}
}

当您运行此应用程序时，它将发出错误，因为MVC框架无法确定应为请求选择哪种操作方法。

让我们使用以下代码指定HttpGet ActionVerb以及您想要作为响应的Action。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
namespace MVCControllerDemo.Controllers {
public class EmployeeController : Controller{
//GET: Employee
//public ActionResult Index()
//{
//return View();
//}
  </span><span class="kwd">public</span><span class="pln"> </span><span class="typ">ActionResult</span><span class="pln"> </span><span class="typ">Search</span><span class="pun">(</span><span class="kwd">string</span><span class="pln"> name</span><span class="pun">){</span><span class="pln">
     </span><span class="kwd">var</span><span class="pln"> input </span><span class="pun">=</span><span class="pln"> </span><span class="typ">Server</span><span class="pun">.</span><span class="typ">HtmlEncode</span><span class="pun">(</span><span class="pln">name</span><span class="pun">);</span><span class="pln">
     </span><span class="kwd">return</span><span class="pln"> </span><span class="typ">Content</span><span class="pun">(</span><span class="pln">input</span><span class="pun">);</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">
	
  </span><span class="pun">[</span><span class="typ">HttpGet</span><span class="pun">]</span><span class="pln">
  </span><span class="kwd">public</span><span class="pln"> </span><span class="typ">ActionResult</span><span class="pln"> </span><span class="typ">Search</span><span class="pun">(){</span><span class="pln">
     </span><span class="kwd">var</span><span class="pln"> input </span><span class="pun">=</span><span class="pln"> </span><span class="str">"Another Search action"</span><span class="pun">;</span><span class="pln">
     </span><span class="kwd">return</span><span class="pln"> </span><span class="typ">Content</span><span class="pun">(</span><span class="pln">input</span><span class="pun">);</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">

}
}

当您运行此应用程序时，您将收到以下输出。

无涯教程-ASP.NET MVC - 选择器

ActionName

NonAction

ActionVerbs

参考链接