System.Web.Caching.Cache 的到期时间是多久？

[YSEE]

System.Web.Caching.Cache



如

Cache["aaa"] = "aa";

这样用 的默认到期时间 是？或者 什么时候失效？

[孟子E章]

默认是没有到期时间，应该是内存不足或者重启程序才会到期删除

[无心雨云]

默认的不知道
不过你可以设置啊

[YSEE]

我就是想知道下 不设置的 后果。
C#的回收机制 是否会清理 还是什么~？

[fellowcheng]

好像是会话有效

[孟子E章]

不设置就是一直占用内存。回收机制一般不会删除Cache

默认时间是
absoluteExpiration 参数设置为等于 MaxValue，后者是表示最大可能的 DateTime 值 12/31/9999 11:59:59 PM 的常数。

[孟子E章]

不过，Cache跟内存有关系，所以使用的时候应该先进行判断if(Cache["x"] != null)

另外， .net 4.0的Cache可以自己定义了，可以存储在文件系统中，不受内存的影响

[孟子E章]

下面是网上的一段文字，讲述了关于 Cache的一些知识

There is some additional information that you should be aware of regarding cache configuration.

* If the worker process private bytes limit is not set, the cache will use one of the following limits:
o x86 2GB: 800MB or 60% of physical RAM, whichever is less
o x86 3GB: 1800MB or 60% of physical RAM, whichever is less
o x64: 1 terabyte or 60% of physical RAM, whichever is less
* If both the worker process private bytes limit and <cache privateBytesLimit/> are set, the cache will use the minimum of the two.
* Just like in 1.x, we drop cache entries and call GC.Collect for two reasons:
o We are very close to the private bytes limit
o The available memory is near or less than 10%
* You can effectively disable trim and cache for low available memory conditions by setting <cache percentagePhysicalMemoryUseLimit/> to 100.
* Unlike 1.x, 2.0 will suspend the trim and collect calls if the last GC.Collect did not reduce private bytes or the size of the managed heaps by more than 1% of the (cache) memory limit.