[Asp.net mvc]OutputCacheAttribute

什么是Cache？

缓存在web应用中是一种以空间换去时间的技术，把频繁访问并且不经常变化的数据存储到内存中，以达到快速访问的目的。在web应用中是比较常见的优化方式。

OutputCacheAttribute

表示一个特性，该特性用于标记将缓存其输出的操作方法。

OutpuCacheAttribute定义

代码片段

[AttributeUsageAttribute(AttributeTargets.Class|AttributeTargets.Method, Inherited = true, 
    AllowMultiple = false)]
public class OutputCacheAttribute : ActionFilterAttribute, 
    IExceptionFilter

从上面的代码中可以看到该特性可以应用在类，方法上面。在mvc中，就可以直接在控制器上面或者控制器中的Action上面直接使用，做到细粒度的对缓存的控制。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace Wolfy.OutputCacheDemo.Controllers
{
    [OutputCache(Duration = 10)]
    public class HomeController : Controller
    {
        // GET: Home
        public string Index()
        {
            return DateTime.Now.ToString();
        }
    }
}

上面的代码是将OutputCache特性标记在了控制器类上，以达到该控制器上所有的Action都将应用该特性，过期时间设置为10s。10s后缓存过期，再访问就会更新时间。

OutputCache特性也可以设置在Action方法上面，以达到更细粒度的控制缓存。

代码片段

    public class HomeController : Controller
    {
        [OutputCache(Duration = 10)]
        // GET: Home
        public string Index()
        {
            return DateTime.Now.ToString();
        }
    }

此时，只有Index的页面进行了缓存。

WebConfig

如果多个控制器或者Action使用相同的缓存配置，可以在配置文件中进行统一配置。

  <system.web>
    <caching>
      <outputCacheSettings>
        <outputCacheProfiles >
          <add name='myoutputcache' duration='10'/>
        </outputCacheProfiles>
      </outputCacheSettings>
    </caching>
    <compilation debug="true" targetFramework="4.5"/>
    <httpRuntime targetFramework="4.5"/>
  </system.web>

应用名称为myoutputcache的缓存

    public class HomeController : Controller
    {
        [OutputCache(CacheProfile = "myoutputcache")]
        // GET: Home
        public string Index()
        {
            return DateTime.Now.ToString();
        }
    }

Note：

当控制器和Action同时使用了OutputCache特性时，以Action为主。

OutputCache参数

#region Assembly System.Web.Mvc.dll, v5.2.2.0
#endregion

using System;
using System.Web.UI;

namespace System.Web.Mvc
{
    // Summary:
    //     Represents an attribute that is used to mark an action method whose output
    //     will be cached.
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, Inherited = true, AllowMultiple = false)]
    public class OutputCacheAttribute : ActionFilterAttribute, IExceptionFilter
    {
        // Summary:
        //     Initializes a new instance of the System.Web.Mvc.OutputCacheAttribute class.
        public OutputCacheAttribute();

        // Summary:
        //     Gets or sets the cache profile name.
        //
        // Returns:
        //     The cache profile name.
        public string CacheProfile { get; set; }
        //
        // Summary:
        //     Gets or sets the child action cache.
        //
        // Returns:
        //     The child action cache.
        public static System.Runtime.Caching.ObjectCache ChildActionCache { get; set; }
        //
        // Summary:
        //     Gets or sets the cache duration, in seconds.
        //
        // Returns:
        //     The cache duration.
        public int Duration { get; set; }
        //
        // Summary:
        //     Gets or sets the location.
        //
        // Returns:
        //     The location.
        public OutputCacheLocation Location { get; set; }
        //
        // Summary:
        //     Gets or sets a value that indicates whether to store the cache.
        //
        // Returns:
        //     true if the cache should be stored; otherwise, false.
        public bool NoStore { get; set; }
        //
        // Summary:
        //     Gets or sets the SQL dependency.
        //
        // Returns:
        //     The SQL dependency.
        public string SqlDependency { get; set; }
        //
        // Summary:
        //     Gets or sets the vary-by-content encoding.
        //
        // Returns:
        //     The vary-by-content encoding.
        public string VaryByContentEncoding { get; set; }
        //
        // Summary:
        //     Gets or sets the vary-by-custom value.
        //
        // Returns:
        //     The vary-by-custom value.
        public string VaryByCustom { get; set; }
        //
        // Summary:
        //     Gets or sets the vary-by-header value.
        //
        // Returns:
        //     The vary-by-header value.
        public string VaryByHeader { get; set; }
        //
        // Summary:
        //     Gets or sets the vary-by-param value.
        //
        // Returns:
        //     The vary-by-param value.
        public string VaryByParam { get; set; }

        // Summary:
        //     Returns a value that indicates whether a child action cache is active.
        //
        // Parameters:
        //   controllerContext:
        //     The controller context.
        //
        // Returns:
        //     true if the child action cache is active; otherwise, false.
        public static bool IsChildActionCacheActive(ControllerContext controllerContext);
        //
        // Summary:
        //     This method is an implementation of System.Web.Mvc.IActionFilter.OnActionExecuted(System.Web.Mvc.ActionExecutedContext)
        //     and supports the ASP.NET MVC infrastructure. It is not intended to be used
        //     directly from your code.
        //
        // Parameters:
        //   filterContext:
        //     The filter context.
        public override void OnActionExecuted(ActionExecutedContext filterContext);
        //
        // Summary:
        //     This method is an implementation of System.Web.Mvc.IActionFilter.OnActionExecuting(System.Web.Mvc.ActionExecutingContext)
        //     and supports the ASP.NET MVC infrastructure. It is not intended to be used
        //     directly from your code.
        //
        // Parameters:
        //   filterContext:
        //     The filter context.
        public override void OnActionExecuting(ActionExecutingContext filterContext);
        //
        // Summary:
        //     This method is an implementation of System.Web.Mvc.IExceptionFilter.OnException(System.Web.Mvc.ExceptionContext)
        //     and supports the ASP.NET MVC infrastructure. It is not intended to be used
        //     directly from your code.
        //
        // Parameters:
        //   filterContext:
        //     The filter context.
        public void OnException(ExceptionContext filterContext);
        //
        // Summary:
        //     This method is an implementation of System.Web.Mvc.IResultFilter.OnResultExecuted(System.Web.Mvc.ResultExecutedContext)
        //     and supports the ASP.NET MVC infrastructure. It is not intended to be used
        //     directly from your code.
        //
        // Parameters:
        //   filterContext:
        //     The filter context.
        public override void OnResultExecuted(ResultExecutedContext filterContext);
        //
        // Summary:
        //     Called before the action result executes.
        //
        // Parameters:
        //   filterContext:
        //     The filter context, which encapsulates information for using System.Web.Mvc.AuthorizeAttribute.
        //
        // Exceptions:
        //   System.ArgumentNullException:
        //     The filterContext parameter is null.
        public override void OnResultExecuting(ResultExecutingContext filterContext);
    }
}

常用的属性

CacheProfile：缓存使用的配置文件的缓存名称。

Duration：缓存时间，以秒为单位，这个除非你的Location=None，可以不添加此属性，其余时候都是必须的。

OutputCacheLocation：枚举类型，缓存的位置。当设置成None时，所有缓存将失效，默认为Any。

namespace System.Web.UI
{
    // Summary:
    //     Specifies the valid values for controlling the location of the output-cached
    //     HTTP response for a resource.
    public enum OutputCacheLocation
    {
        // Summary:
        //     The output cache can be located on the browser client (where the request
        //     originated), on a proxy server (or any other server) participating in the
        //     request, or on the server where the request was processed. This value corresponds
        //     to the System.Web.HttpCacheability.Public enumeration value.
        Any = 0,
        //
        // Summary:
        //     The output cache is located on the browser client where the request originated.
        //     This value corresponds to the System.Web.HttpCacheability.Private enumeration
        //     value.
        Client = 1,
        //
        // Summary:
        //     The output cache can be stored in any HTTP 1.1 cache-capable devices other
        //     than the origin server. This includes proxy servers and the client that made
        //     the request.
        Downstream = 2,
        //
        // Summary:
        //     The output cache is located on the Web server where the request was processed.
        //     This value corresponds to the System.Web.HttpCacheability.Server enumeration
        //     value.
        Server = 3,
        //
        // Summary:
        //     The output cache is disabled for the requested page. This value corresponds
        //     to the System.Web.HttpCacheability.NoCache enumeration value.
        None = 4,
        //
        // Summary:
        //     The output cache can be stored only at the origin server or at the requesting
        //     client. Proxy servers are not allowed to cache the response. This value corresponds
        //     to the combination of the System.Web.HttpCacheability.Private and System.Web.HttpCacheability.Server
        //     enumeration values.
        ServerAndClient = 5,
    }
}

VaryByParam：用于多个输出缓存的字符串列表，并以分号进行分隔。默认时，该字符串与GET方法传递的参数或与POST方法传递的变量相对应。当被设置为多个参数时，输出缓存将会为每个参数都准备一个与之相对应的文档版本。可能值包括none，*，以及任何有效的查询串或POST参数名称。

结语

由于没找到缓存依赖mysql的办法，关于OutputCache的内容就先到这里。

关于缓存依赖的内容，可参考这篇文章

http://www.cnblogs.com/iamlilinfeng/p/4419362.html