ASP.NET Cache类 使用方式

1、将值直接写入Cache

HttpContext.Current.Cache["One"] = "1";

使用'绝对过期'方式处理缓存，过期时间为：9999年12月31日 (不推荐使用该方法处理缓存，并且应在适当的时候清空缓存Key)

 

2、使用Insert(String, Object)插入Cache

string cacheKey = "Two";
object cacheValue = HttpContext.Current.Cache.Get(cacheKey);

if(cacheValue == null)
{
    cacheValue = WebConfigurationManager.ConnectionStrings["ApplicationServices"].ConnectionString;

    HttpContext.Current.Cache.Insert(cacheKey, cacheValue);
}

//显示指定缓存的Key 与 Value
this.ShowMessage(cacheKey, cacheValue.ToString());

 

3、使用Insert(String, Object, CacheDependency, DateTime, TimeSpan)插入Cache

string cacheKey = "__cache__students";

DataSet dataSet = this.Cache.Get(cacheKey) as DataSet;

if(dataSet == null)
{
    dataSet = new DataSet();

    //加载XML并填充至DataSet
    dataSet.ReadXml(this.Server.MapPath(@"XMLFile.xml"));

    //加入缓存，并设定'绝对过期时间'为5分钟
    this.Cache.Insert(cacheKey, dataSet, null, DateTime.Now.AddMinutes(5), System.Web.Caching.Cache.NoSlidingExpiration);
}

//绑定DataGrid数据
grdDefault.DataSource = dataSet;
grdDefault.DataBind();

该方法较重要的两个参数为absoluteExpiration及slidingExpiration
absoluteExpiration  DateTime类型，代表绝对过期时间
slidingExpiration  TimeSpan类型，代表滑动过期时间
absoluteExpiration与slidingExpiration不能同时使用
例如：设定了absoluteExpiration参数时，slidingExpiration必须设定为System.Web.Caching.Cache.NoSlidingExpiration
反之：设定了slidingExpiration参数时，absoluteExpiration必须设定为System.Web.Caching.Cache.NoAbsoluteExpiration

 

4、使用Insert(String, Object, CacheDependency, DateTime, TimeSpan, CacheItemPriority, CacheItemRemovedCallback)插入Cache

public partial class PriorityAndCallbackDemo : System.Web.UI.Page
{
    #region 静态字段
    static bool CacheItemRemoved = false;
    static CacheItemRemovedReason Reason;
    static string CacheItemKey = "fw__cache__students";
    #endregion

    #region 事件处理
    //页面加载
    protected void Page_Load(object sender, EventArgs e)
    {
        //缓存项已移除
        if(PriorityAndCallbackDemo.CacheItemRemoved)
        {
            ltMessage.Text = string.Format("Key={0}已从缓存移出，原因为：{1}", PriorityAndCallbackDemo.CacheItemKey, PriorityAndCallbackDemo.Reason.ToString());
        }
    }

    //'添加缓存'按钮 点击事件 处理
    protected void btnAddCache_Click(object sender, EventArgs e)
    {
        DataSet dataSet = this.Cache.Get(PriorityAndCallbackDemo.CacheItemKey) as DataSet;

        if(dataSet == null)
        {
            dataSet = new DataSet();
            dataSet.ReadXml(this.Server.MapPath(@"XMLFile.xml"));

            //使用 Web.config 作为缓存过期依赖项
            CacheDependency dependency = new CacheDependency(this.Server.MapPath(@"Web.config"), DateTime.Now);

            //加入缓存，设定优先级为默认级别
            this.Cache.Insert(PriorityAndCallbackDemo.CacheItemKey, dataSet, dependency, DateTime.Now.AddMinutes(1), System.Web.Caching.Cache.NoSlidingExpiration, CacheItemPriority.Default, new CacheItemRemovedCallback(this.CacheItemRemovedHandler));
        }

        //绑定GridView数据
        grdDefault.DataSource = dataSet;
        grdDefault.DataBind();
    }

    //'移除缓存'按钮 点击事件 处理
    protected void btnRemoveCache_Click(object sender, EventArgs e)
    {
        if(this.Cache[PriorityAndCallbackDemo.CacheItemKey] != null)
        {
            this.Cache.Remove(PriorityAndCallbackDemo.CacheItemKey);
        }
    }
    #endregion

    #region 私有方法
    //缓存项移除事件处理
    private void CacheItemRemovedHandler(string key, object value, CacheItemRemovedReason relason)
    {
        PriorityAndCallbackDemo.CacheItemRemoved = true;
        PriorityAndCallbackDemo.Reason = relason;
    }
    #endregion
}

该方法较重要的两个参数为CacheItemPriority及CacheItemRemovedCallback
CacheItemPriority  缓存项优先级，当服务器内存不够时，优先级越高的项越不容易被移除
CacheItemRemovedCallback  该参数为委托类型，当缓存项被移除时所调用，包含Reason参数用于表示缓存项被移除的原因