MemoryCacheHelper 缓存类
public partial class MemoryCacheHelper
{
private static object _locker = new object();
private static MemoryCacheHelper instance;
//委托移除以后
private CacheEntryRemovedCallback _RemovedCallback;
//委托即将移除时
private CacheEntryUpdateCallback _UpdateCallback;
private MemoryCacheHelper()
{
}
public static MemoryCacheHelper Instance
{
get
{
if (instance == null)
{
lock (_locker)
{
if (instance == null)
{
instance = new MemoryCacheHelper();
}
}
}
return instance;
}
}
/// <summary>
/// 获取缓存中的值
/// </summary>
/// <typeparam name="T">类型</typeparam>
/// <param name="key">标识的Key(保持唯一)</param>
/// <param name="value">需要缓存的缓存项的值</param>
/// <param name="slidingExpiration">该值指示如果某个缓存项在给定时段内未被访问，是否应被逐出</param>
/// <param name="absoluteExpiration">该值指示是否应在指定持续时间过后逐出某个缓存项</param>
/// <returns></returns>
public T GetCacheItem<T>(string key, T value, TimeSpan? slidingExpiration = null, DateTime? absoluteExpiration = null)
{
return GetCacheItem<T>(key, value, null, slidingExpiration, absoluteExpiration);
}
/// <summary>
/// 获取缓存中的值
/// </summary>
/// <typeparam name="T">类型</typeparam>
/// <param name="key">标识的Key(保持唯一)</param>
/// <param name="value">需要缓存的缓存项的值</param>
/// <param name="Command">SQL执行的Command</param>
/// <param name="slidingExpiration">该值指示如果某个缓存项在给定时段内未被访问，是否应被逐出</param>
/// <param name="absoluteExpiration">该值指示是否应在指定持续时间过后逐出某个缓存项</param>
/// <returns></returns>
public T GetCacheItem<T>(string key, T value, SqlCommand Command = null, TimeSpan? slidingExpiration = null, DateTime? absoluteExpiration = null)
{
if (string.IsNullOrWhiteSpace(key))
throw new ArgumentException("Invalid cache key");
if (value == null)
throw new ArgumentNullException("value");
if (slidingExpiration == null && absoluteExpiration == null)
throw new ArgumentException("Either a sliding expiration or absolute must be provided");
ObjectCache cachelist = MemoryCache.Default;
if (cachelist[key] == null)
{
lock (_locker)
{
var item = new CacheItem(key, value);
var policy = CreatePolicy(_RemovedCallback, _UpdateCallback, Command, slidingExpiration, absoluteExpiration);
MemoryCache.Default.Add(item, policy);
}
}
return (T)Convert.ChangeType(cachelist[key], typeof(T));
}
/// <summary>
/// 获取缓存中的值
/// </summary>
/// <typeparam name="T">类型</typeparam>
/// <param name="key">标识的Key(保持唯一)</param>
public T GetCacheItem<T>(string key)
{
if (string.IsNullOrWhiteSpace(key))
throw new ArgumentException("Invalid cache key");
ObjectCache cachelist = MemoryCache.Default;
return (T)Convert.ChangeType(cachelist[key], typeof(T));
}
/// <summary>
/// 创建指定缓存项的一组逐出和过期详细信息
/// </summary>
/// <param name="RemovedCallback">在从缓存中移除某个项后将调用该委托</param>
/// <param name="UpdateCallback">在从缓存中移除某个缓存项之前将调用该委托</param>
/// <param name="slidingExpiration">该值指示如果某个缓存项在给定时段内未被访问，是否应被逐出</param>
/// <param name="absoluteExpiration">该值指示是否应在指定持续时间过后逐出某个缓存项</param>
/// <returns></returns>
private CacheItemPolicy CreatePolicy(CacheEntryRemovedCallback RemovedCallback, CacheEntryUpdateCallback UpdateCallback, SqlCommand Command, TimeSpan? slidingExpiration, DateTime? absoluteExpiration)
{
var policy = new CacheItemPolicy();
if (absoluteExpiration.HasValue)
policy.AbsoluteExpiration = absoluteExpiration.Value;
else if (slidingExpiration.HasValue)
policy.SlidingExpiration = slidingExpiration.Value;
policy.Priority = CacheItemPriority.Default;
if (RemovedCallback != null)
policy.RemovedCallback = RemovedCallback;
if (UpdateCallback != null)
policy.UpdateCallback = UpdateCallback;
if (Command != null)
{
System.Data.SqlClient.SqlDependency mSqlDependency = new System.Data.SqlClient.SqlDependency(Command);
policy.ChangeMonitors.Add(new SqlChangeMonitor(mSqlDependency));
}
return policy;
}
/// <summary>
/// 事件定义在从缓存中移除某个缓存项后触发
/// </summary>
public event CacheEntryRemovedCallback RemovedCallback
{
add
{
lock (_locker)
{
_RemovedCallback += value;
}
}
remove
{
lock (_locker)
{
_RemovedCallback -= value;
}
}
}
/// <summary>
/// 事件定义在从缓存中即将移除某个缓存项时触发
/// </summary>
public event CacheEntryUpdateCallback UpdateCallback
{
add
{
lock (_locker)
{
_UpdateCallback += value;
}
}
remove
{
lock (_locker)
{
_UpdateCallback -= value;
}
}
}
/// <summary>
/// 定义在从缓存中移除某个缓存项后触发
/// </summary>
/// <param name="args">有关已从缓存中移除的缓存项的信息</param>
protected virtual void OnRemovedCallback(CacheEntryRemovedArguments args)
{
if(_RemovedCallback!=null)
_RemovedCallback(args);
}
/// <summary>
/// 定义在从缓存中即将移除某个缓存项时触发
/// </summary>
/// <param name="args">有关将从缓存中移除的缓存项的信息</param>
protected virtual void OnUpdateCallback(CacheEntryUpdateArguments args)
{
if (_UpdateCallback != null)
_UpdateCallback(args);
}
}