文件依赖缓存的运用
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO ;
using System.Xml ;
using System.Web.Caching ;
using System.Threading ;
namespace BasicCompent
{
public class PageCssProvider
{
static System.Web.HttpContext cxt;
static ManualResetEvent mr = new ManualResetEvent(true);
static ManualResetEvent mw = new ManualResetEvent(true);
static XmlDocument _doc;
private PageCssProvider()
{
}
static PageCssProvider()
{
cxt = System.Web.HttpContext.Current;
Init();
}
public static string PageCss(string pageName)
{
if (string.IsNullOrEmpty(pageName))
return string.Empty;
string xmpath = string.Format("/pages/page[@name=/"{0}/"]", pageName);
mw.WaitOne();
mr.Reset();
try
{
if(_doc ==null )
return string.Empty ;
XmlNode node = _doc.SelectSingleNode(xmpath);
return node.InnerXml;
}
finally
{
mr.Set();
}
}
static void Init()
{
mr.WaitOne();
mw.Reset();
try
{
string realPath = cxt.Server.MapPath("~/Css.xml");
if (!File.Exists(realPath))
return;
_doc = new XmlDocument();
_doc.Load(realPath);
CacheDependency cd = new CacheDependency(realPath);
cxt.Cache.Insert("pageCss", realPath, cd, Cache.NoAbsoluteExpiration,
Cache.NoSlidingExpiration, CacheItemPriority.NotRemovable, reportRemovedCallback);
}
finally
{
mw.Set();
}
}
static void reportRemovedCallback(String key, object value, CacheItemRemovedReason reason)
{
Init();
}
}
}
