C#缓存

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime;
using System.Runtime.Caching;

namespace BD.EAS_jinantianhui
{
public class CacheHelper
{
private static readonly Object _locker = new object();

public static T GetCacheItem<T>(String key, Func<T> cachePopulate, TimeSpan? slidingExpiration = null, DateTime? absoluteExpiration = null)
{
if (String.IsNullOrWhiteSpace(key)) throw new ArgumentException("Invalid cache key");
if (cachePopulate == null) throw new ArgumentNullException("cachePopulate");
if (slidingExpiration == null && absoluteExpiration == null) throw new ArgumentException("Either a sliding expiration or absolute must be provided");

if (MemoryCache.Default[key] == null)
{
lock (_locker)
{
if (MemoryCache.Default[key] == null)
{
var item = new CacheItem(key, cachePopulate());
var policy = CreatePolicy(slidingExpiration, absoluteExpiration);

MemoryCache.Default.Add(item, policy);
}
}
}

return (T)MemoryCache.Default[key];
}

private static CacheItemPolicy CreatePolicy(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;

return policy;
}
// <summary>
/// 清空缓存
/// </summary>
public static void ClearCache()
{
List<string> cacheKeys = MemoryCache.Default.Select(kvp => kvp.Key).ToList();
foreach (string cacheKey in cacheKeys)
{
MemoryCache.Default.Remove(cacheKey);
}
}
}
}

使用方式：

WSContext context = MemoryCache.Default["WSContext"] as WSContext;
if (null == context)
{
context = service.login(easUser, easPass, "eas", easCRMdata, "L2", int.Parse(easDBType));
if (null != context)
{
CacheHelper.GetCacheItem<WSContext>("WSContext", delegate () { return context; }, new TimeSpan(0, 30, 0));//30分钟过期
return context;
}
}
return context;