ASP.NET缓存应用：CacheItemRemovedCallback 委托
CacheItemRemovedCallback 定义在从 Cache 移除缓存项时通知应用程序的回调方法。
命名空间： System.Web.Caching
程序集： System.Web（在 System.Web.dll 中）
参数
key
类型：System..::.String
从缓存中移除的键。
value
类型：System..::.Object
与从缓存中移除的键关联的 Object 项。
reason
类型：System.Web.Caching..::.CacheItemRemovedReason
CacheItemRemovedReason 枚举指定的、从缓存移除项的原因。
示例：
<html>
<Script runat=server language="C#">
static bool itemRemoved = false;
static CacheItemRemovedReason reason;
CacheItemRemovedCallback onRemove = null;
public void RemovedCallback(String k, Object v, CacheItemRemovedReason r){
itemRemoved = true;
reason = r;
}
public void AddItemToCache(Object sender, EventArgs e) {
itemRemoved = false;
onRemove = new CacheItemRemovedCallback(this.RemovedCallback);
if (Cache["Key1"] == null)
Cache.Add("Key1", "Value 1", null, DateTime.Now.AddSeconds(60), Cache.NoSlidingExpiration, CacheItemPriority.High, onRemove);
}
public void RemoveItemFromCache(Object sender, EventArgs e) {
if(Cache["Key1"] != null)
Cache.Remove("Key1");
}
</Script>
<body>
<Form runat="server">
<input type=submit OnServerClick="AddItemToCache" value="Add Item To Cache" runat="server"/>
<input type=submit OnServerClick="RemoveItemFromCache" value="Remove Item From Cache" runat="server"/>
</Form>
<% if (itemRemoved) {
Response.Write("RemovedCallback event raised.");
Response.Write("<BR>");
Response.Write("Reason: <B>" + reason.ToString() + "</B>");
}
else {
Response.Write("Value of cache key: <B>" + Server.HtmlEncode(Cache["Key1"] as string) + "</B>");
}
%>
</body>
</html>