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HttpContext.Current.Cache和HttpRuntime.Cache的区别，以及System.Runtime.Caching
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先看MSDN上的解释：
HttpContext.Current.Cache：为当前 HTTP 请求获取Cache对象。
HttpRuntime.Cache：获取当前应用程序的Cache。
我们再用.NET Reflector工具看看HttpContext.Cache和HttpRuntime.Cache的实现：
HttpContext.Cache和HttpRuntime.Cache实现
//System.Web.HttpContext.Cache属性实现
public sealed class HttpContext
{
public Cache Cache
{
get
{
return HttpRuntime.Cache;
}
}
}
//System.Web.HttpRuntime.Cache属性实现
public sealed class HttpRuntime
{
public static Cache Cache
{
get
{
if (AspInstallDirectoryInternal == null)
{
throw new HttpException(SR.GetString("Aspnet_not_installed", new object[] { VersionInfo.SystemWebVersion }));
}
Cache cache = _theRuntime._cachePublic;
if (cache == null)
{
CacheInternal cacheInternal = CacheInternal;
CacheSection cacheSection = RuntimeConfig.GetAppConfig().Cache;
cacheInternal.ReadCacheInternalConfig(cacheSection);
_theRuntime._cachePublic = cacheInternal.CachePublic;
cache = _theRuntime._cachePublic;
}
return cache;
}
}
}
通过上面的代码我们可以看出：HttpContext.Current.Cache是调用HttpRuntime.Cache实现的，两者指向同一Cache对象。那么两者到底有没有区别的？既然两个指向的是同一Cache对象，两者的差别只能出现在HttpContext和HttpRuntime上了。我们再来看看MSDN中HttpContext和HttpRuntime的定义。
HttpContext：封装有关个别HTTP请求的所有HTTP特定的信息，HttpContext.Current为当前的HTTP请求获取HttpContext对象。
HttpRuntime：为当前应用程序提供一组ASP.NET运行时服务。
由上面的定义可以看出：HttpRuntime.Cache相当于就是一个缓存具体实现类，这个类虽然被放在了System.Web命名空间下，但是非Web应用下也是可以使用；HttpContext.Current.Cache是对上述缓存类的封装，由于封装到了HttpContext类中，局限于只能在知道HttpContext下使用，即只能用于Web应用。
下面的例子可以很好的说明这一点：
HttpContext.Cache和HttpRuntime.Cache的示例
class CacheTest
{
static void Main(string[] args)
{
System.Web.Caching.Cache httpRuntimeCache = System.Web.HttpRuntime.Cache;
httpRuntimeCache.Insert("httpRuntimeCache", "I am stored in HttpRuntime.Cache");
if (httpRuntimeCache != null)
{
Console.WriteLine("httpRuntimeCache:" + httpRuntimeCache["httpRuntimeCache"]);
}
System.Web.HttpContext httpContext = System.Web.HttpContext.Current;
if (httpContext == null)
{
Console.WriteLine("HttpContext object is null in Console Project");
}
else
{
System.Web.Caching.Cache httpContextCache = httpContext.Cache;
httpContextCache.Insert("httpContextCache", "I am stored in HttpRuntime.Cache");
if (httpContextCache == null)
{
Console.WriteLine("httpContextCache is null");
}
}
Console.ReadLine();
}
}
输出结果：httpRuntimeCache:I am stored in HttpRuntime.Cache
HttpContext object is null in Console Project
综上：我们在使用Cache时，尽量使用HttpRuntime.Cache，既能减少出错，也减少了一次函数调用。
参考资料：HttpRuntime.Cache 与HttpContext.Current.Cache的疑问，HttpRuntime.Cache vs. HttpContext.Current.Cache
出处：http://blog.csdn.net/qwlovedzm/article/details/7024405
===============================================================================
下面我们看看简单的缓存类处理：
using System;
using System.Collections;
using System.Web;
using System.Web.Caching; namespace aaaaa.Api.Business
{
/// <summary>
/// 缓存类
/// </summary>
public class CacheHelper
{
/// <summary>
/// 增加一个缓存对象
/// </summary>
/// <param name="strKey">键值名称</param>
/// <param name="valueObj">被缓存对象</param>
/// <param name="durationMin">缓存失效时间（默认为5分钟）</param>
/// <param name="cachePriority">保留优先级(枚举数值)</param>
/// <returns>缓存写入是否成功true 、false</returns>
public static bool InsertCach(string strKey, object valueObj, int durationMin,
CacheItemPriority cachePriority = CacheItemPriority.Default)
{
TimeSpan ts;
if (!string.IsNullOrWhiteSpace(strKey) && valueObj != null)
{
//onRemove是委托执行的函数，具体方法看下面的onRemove(...)
CacheItemRemovedCallback callBack = new CacheItemRemovedCallback(onRemove);
ts = durationMin == ? new TimeSpan(, , ) : new TimeSpan(, durationMin, );
//HttpContext.Current.Cache.Insert(
HttpRuntime.Cache.Insert(
strKey,
valueObj,
null,
DateTime.Now.Add(ts),
Cache.NoSlidingExpiration,
cachePriority,
callBack
);
return true;
}
else
{
return false;
}
} /// <summary>
/// 判断缓存对象是否存在
/// </summary>
/// <param name="strKey">缓存键值名称</param>
/// <returns>是否存在true 、false</returns>
public static bool IsExist(string strKey)
{
//return HttpContext.Current.Cache[strKey] != null;
return HttpRuntime.Cache.Get(strKey) != null;
} /// <summary>
/// 读取缓存对象
/// </summary>
/// <param name="strKey">缓存键值名称</param>
/// <returns>缓存对象，objec类型</returns>
public static object GetCache(string strKey)
{
//if (HttpContext.Current.Cache[strKey] != null)
if (IsExist(strKey))
{
object obj = HttpRuntime.Cache.Get(strKey);
return obj ?? null;
}
else
{
return null;
}
} /// <summary>
/// 移除缓存对象
/// </summary>
/// <param name="strKey">缓存键值名称</param>
public static void Remove(string strKey)
{
//if (HttpContext.Current.Cache[strKey] != null)
if (IsExist(strKey))
{
HttpRuntime.Cache.Remove(strKey);
}
} /// <summary>
/// 清除所有缓存
/// </summary>
public static void Clear()
{
IDictionaryEnumerator enu = HttpRuntime.Cache.GetEnumerator();
while (enu.MoveNext())
{
Remove(enu.Key.ToString());
}
} public static CacheItemRemovedReason reason;
/// <summary>
/// 此方法在值失效之前调用，可以用于在失效之前更新数据库，或从数据库重新获取数据
/// </summary>
/// <param name="strKey"></param>
/// <param name="obj"></param>
/// <param name="reason"></param>
private static void onRemove(string strKey, object obj, CacheItemRemovedReason r)
{
reason = r;
} //... }
}
出处：http://blog.csdn.net/joyhen/article/details/40379145
=======================================================================
引用：System.Runtime.Caching.dll，如下测试，fm4.5
static void CacheTest()
{
string cname = "filescontents";
ObjectCache cc = MemoryCache.Default;
string fileContents = cc[cname] as string; if (fileContents == null)
{
CacheItemPolicy policy = new CacheItemPolicy(); TimeSpan sp = new TimeSpan(, , );
policy.SlidingExpiration = sp; List<string> filePaths = new List<string>();
string path = System.IO.Directory.GetCurrentDirectory() + "\\example.txt";
filePaths.Add(path); policy.ChangeMonitors.Add(new HostFileChangeMonitor(filePaths)); fileContents = System.IO.File.ReadAllText(path, Encoding.Default);
cc.Set(cname, fileContents, policy);
} Console.WriteLine(fileContents);
} static void Main(string[] args)
{
//ExecuteCode(WriteData);
//ExecuteCode(ReadData);
//ExecuteCode(TransData);
bool quit = false;
while (!quit)
{
Console.Write("get cache: ");
string demo = Console.ReadLine();
switch (demo)
{
case "Y": ExecuteCode(CacheTest); break;
case "Q":
quit = true;
break;
default:
Console.WriteLine("Choose a Word of Y and Q(to quit)");
break;
}
}
Console.ReadKey();
} public static void ExecuteCode(Action a)
{
System.Diagnostics.Stopwatch stopwatch = new System.Diagnostics.Stopwatch();
stopwatch.Start(); a(); stopwatch.Stop();
TimeSpan timespan = stopwatch.Elapsed; Console.WriteLine("运行{0}秒", timespan.TotalSeconds);
}
出处：http://blog.csdn.net/joyhen/article/details/39990455
