缓存类 和说明

using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;
using System.Web;
using System.Web.Caching;

namespace My.Bll
{
public class BllCache
{
/*
//由 CacheItemPriority 枚举表示。缓存在退出对象时使用该值；具有较低成本的对象在具有较高成本的对象之前被从缓存移除。
//public enum CacheItemPriority
//{
// AboveNormal = 4,
// BelowNormal = 2,
// Default = 3,
// High = 5,
// Low = 1,
// Normal = 3,
// NotRemovable = 6
//}
* 如果 Cache 中已保存了具有相同 key 参数的项，则对此方法的调用将失败。若要使用相同的 key 参数覆盖现有的 Cache 项，请使用 Insert 方法。

无法同时设置 absoluteExpiration 和 slidingExpiration 参数。如果要让缓存项在特定时间到期，可将 absoluteExpiration 参数设置为特定时间，并将 slidingExpiration 参数设置为 NoSlidingExpiration。

如果要让缓存项在最后一次访问该项后的某段时间之后到期，可将 slidingExpiration 参数设置为到期间隔，并将 absoluteExpiration 参数设置为 NoAbsoluteExpiration。
//add和Insert的差别是
//public void Insert(string key, object value, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration)
//{
// DateTime utcAbsoluteExpiration = DateTimeUtil.ConvertToUniversalTime(absoluteExpiration);
// this._cacheInternal.DoInsert(true, key, value, dependencies, utcAbsoluteExpiration, slidingExpiration, CacheItemPriority.Normal, null, true);
//}

//public object Add(string key, object value, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback)
//{
// DateTime utcAbsoluteExpiration = DateTimeUtil.ConvertToUniversalTime(absoluteExpiration);
// return this._cacheInternal.DoInsert(true, key, value, dependencies, utcAbsoluteExpiration, slidingExpiration, priority, onRemoveCallback, false);
//}
*/





/// <summary>
///缓存对象
/// </summary>
protected static volatile Cache webCache = HttpRuntime.Cache;//( volatile)编译器就老老实实的每次都从内存中读取这个变量值,不是在CPU的缓存里读

/// <summary>
/// 获取数据缓存
/// </summary>
/// <param name="CacheKey">键</param>
public static object GetCache(string CacheKey)
{
if (CacheKey == null && CacheKey.Length == 0)
return null;
return webCache.Get(CacheKey);
}


/********************************************时间偏差的缓存*****************************************************************/
/*
*
* 使用时间偏差内的缓存的意思是在缓存创建后slidingExpiration时间偏差内连续访问缓存项的话继续保持指定缓存项对象
 * 用 偏差 过期的缓存absoluteExpiration参数要设置NoAbsoluteExpiration，NoAbsoluteExpiration是DateTime.MaxValue的意思
* 就要slidingExpiration时间偏差内连续访问的话连续缓存，如果在slidingExpiration时间偏差内没人用缓存项拿删除
* static Cache()
{
NoAbsoluteExpiration = DateTime.MaxValue;
NoSlidingExpiration = TimeSpan.Zero;
s_sentinelRemovedCallback = new CacheItemRemovedCallback(SentinelEntry.OnCacheItemRemovedCallback);
}
*/
/// <summary>
/// 在指定的slidingExpiration时间偏差内连续访问缓存项的话(级别Normal = 3），继续保持指定缓存项对象里加入对象
/// 别的级别（NotRemovable = 6，High = 5,AboveNormal = 4,Normal = 3,BelowNormal = 2,Low = 1）
/// absoluteExpiration=NoAbsoluteExpiration，slidingExpiration=TimeSpan.FromSeconds(expire)
/// </summary>
/// <param name="CacheKey">对象的键值</param>
/// <param name="o">缓存的对象</param>
/// <param name="expire">时间偏差</param>
public static void InsertNormalSlidingCache(string CacheKey, object o, int expire)
{
if (CacheKey == null || CacheKey.Length == 0 || o == null)
{
return;
}
webCache.Insert(CacheKey, o, null, Cache.NoAbsoluteExpiration, TimeSpan.FromSeconds(expire), CacheItemPriority.Normal, null);
}
/// <summary>
/// 在指定的slidingExpiration时间偏差内连续访问缓存项的话(高级别High = 5），继续保持指定缓存项对象里加入对象
/// 别的级别（NotRemovable = 6，High = 5,AboveNormal = 4,Normal = 3,BelowNormal = 2,Low = 1）
/// absoluteExpiration=NoAbsoluteExpiration，slidingExpiration=TimeSpan.FromSeconds(expire)
/// </summary>
/// <param name="CacheKey">对象的键值</param>
/// <param name="o">缓存的对象</param>
/// <param name="expire">时间偏差</param>
public static void InsertHighSlidingCache(string CacheKey, object o, int expire)
{
if (CacheKey == null || CacheKey.Length == 0 || o == null)
{
return;
}
webCache.Insert(CacheKey, o, null, Cache.NoAbsoluteExpiration, TimeSpan.FromSeconds(expire), CacheItemPriority.High, null);
}
/// <summary>
/// 在指定的absoluteExpiration时间偏差内连续访问缓存项的话，继续保持指定缓存项对象里加入对象
/// absoluteExpiration=NoAbsoluteExpiration，absoluteExpiration=TimeSpan.FromSeconds(expire)
/// </summary>
/// <param name="CacheKey">对象的键值</param>
/// <param name="o">缓存的对象</param>
/// <param name="expire">时间偏差</param>
/// <param name="jibie">缓存级别，级别高到低存放内存数据（NotRemovable = 6，High = 5,AboveNormal = 4,Normal = 3,BelowNormal = 2,Low = 1）</param>
public static void InsertSlidingCache(string CacheKey, object o, int expire,int jibie)
{
if (CacheKey == null || CacheKey.Length == 0 || o == null)
{
return;
}
CacheItemPriority dareje;
switch (jibie)
{
case 1: dareje = CacheItemPriority.Low; break;
case 2: dareje = CacheItemPriority.BelowNormal; break;
case 3: dareje = CacheItemPriority.Normal; break;
case 4: dareje = CacheItemPriority.AboveNormal; break;
case 5: dareje = CacheItemPriority.High; break;
case 6: dareje = CacheItemPriority.NotRemovable; break;
default: dareje = CacheItemPriority.Normal; break;
}
webCache.Insert(CacheKey, o, null, Cache.NoAbsoluteExpiration, TimeSpan.FromSeconds(expire), dareje, null);
}
/********************************************绝对过期的缓存*****************************************************************/
/*
*
* 使用绝对过期的缓存的意思是在缓存创建后过了absoluteExpiration时间后缓存过期
* 用绝对过期的缓存slidingExpiration参数要设置TimeSpan.Zero，TimeSpan.Zero是0的意思
* 也就是说没时间偏差
* static Cache()
{
NoAbsoluteExpiration = DateTime.MaxValue;
NoSlidingExpiration = TimeSpan.Zero;
s_sentinelRemovedCallback = new CacheItemRemovedCallback(SentinelEntry.OnCacheItemRemovedCallback);
}
*/


// <summary>
/// 使用绝对过期的缓存中加入当前对象（过了expire时间后缓存过期)
/// </summary>
/// <param name="CacheKey">对象的键值</param>
/// <param name="o">缓存的对象</param>
/// <param name="expire">到期时间,单位:秒(0时最大的时间，高的级别，表示永不过期）</param>
/// <param name="jibie">缓存级别（NotRemovable = 6，High = 5,AboveNormal = 4,Normal = 3,BelowNormal = 2,Low = 1）</param>
public virtual void InsertAbsoluteCache(string CacheKey, object o, int expire,int jibie)
{
if (CacheKey == null || CacheKey.Length == 0 || o == null)
{
return;
}
CacheItemPriority dareje;
switch (jibie)
{
case 1: dareje = CacheItemPriority.Low; break;
case 2: dareje = CacheItemPriority.BelowNormal; break;
case 3: dareje = CacheItemPriority.Normal; break;
case 4: dareje = CacheItemPriority.AboveNormal; break;
case 5: dareje = CacheItemPriority.High; break;
case 6: dareje = CacheItemPriority.NotRemovable; break;
default:dareje = CacheItemPriority.Normal; break;
}
webCache.Insert(CacheKey, o, null, DateTime.Now.AddSeconds(expire), Cache.NoSlidingExpiration, dareje, null);
}
/// <summary>
/// 使用绝对过期的缓存中加入当前对象(级别是Normal）（过了expire时间后缓存过期)
/// </summary>
/// <param name="CacheKey"></param>
/// <param name="o"></param>
/// <param name="expire"></param>
public virtual void InsertAbsoluteNormalCache(string CacheKey, object o, int expire)
{
if (CacheKey == null || CacheKey.Length == 0 || o == null)
{
return;
}
webCache.Insert(CacheKey, o, null, DateTime.Now.AddSeconds(expire), Cache.NoSlidingExpiration, CacheItemPriority.Normal, null);
}

// <summary>
/// 使用绝对过期的缓存中加入当前对象（过了expire时间后过期缓存，absoluteExpiration=DateTime.Now.AddSeconds(expire)）
/// (slidingExpiration 参数设置成 TimeSpan.Zero ，TimeSpan.Zero就是时间差别0的意思TimeSpan.Zero=0）
/// </summary>
/// <param name="CacheKey">对象的键值</param>
/// <param name="o">缓存的对象</param>
/// <param name="expire">到期时间,单位:秒(0时最大的时间，高的级别，表示永不过期）</param>
public virtual void InsertAbsoluteHighCache(string CacheKey, object o, int expire)
{
if (CacheKey == null || CacheKey.Length == 0 || o == null)
{
return;
}
 if (expire == 0)
{
webCache.Insert(CacheKey, o, null, DateTime.MaxValue, TimeSpan.Zero, CacheItemPriority.High, null);
}
else
{
webCache.Insert(CacheKey, o, null, DateTime.Now.AddSeconds(expire), Cache.NoSlidingExpiration, CacheItemPriority.High, null);
}
}

/// <summary>
/// 清空的有缓存数据
/// </summary>
public static void DeleteAllItems()
{
IDictionaryEnumerator CacheEnum = HttpRuntime.Cache.GetEnumerator();
while (CacheEnum.MoveNext())
{
webCache.Remove(CacheEnum.Key.ToString());
}
}
/// <summary>
/// 清空指定字符开头的所有缓存（不分大小写开头）
/// </summary>
/// <param name="prefix">指定字符开头</param>
public static void DeletePrefixItems(string prefix)
{
prefix = prefix.ToLower();
List<string> items_Remove = new List<string>();
IDictionaryEnumerator cache_enum = HttpRuntime.Cache.GetEnumerator();
while (cache_enum.MoveNext())
{
if (cache_enum.Key.ToString().ToLower().StartsWith(prefix))
{
items_Remove.Add(cache_enum.Key.ToString());
}
}
foreach (string i in items_Remove)
{
webCache.Remove(i);
}
}


}
}