add to Cache[Key]=object  or Cache.Insert

remove Cache.Remove(key)

1、 Write the value directly to Cache

The code is as follows Copy code
HttpContext.Current.Cache["One"] = "1";

Use ' Absolute Expiration ' How to handle cache , The expiration date is :9999 year 12 month 31 Japan ( This method is not recommended for caching , And the cache should be cleared at an appropriate time Key)

2、 Use Insert(String, Object) Insert Cache

The code is as follows Copy code
string cacheKey = "Two";
object cacheValue = HttpContext.Current.Cache.Get(cacheKey);

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

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

// Displays the... Of the specified cache Key And Value
this.ShowMessage(cacheKey, cacheValue.ToString());

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

The code is as follows Copy code
string cacheKey = "__cache__students";

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

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

// load XML And fill in DataSet
    dataSet.ReadXml(this.Server.MapPath(@"XMLFile.xml"));

// Join the cache , And set ' Absolute expiration time ' by 5 minute
    this.Cache.Insert(cacheKey, dataSet, null, DateTime.Now.AddMinutes(5), System.Web.Caching.Cache.NoSlidingExpiration);
}

// binding DataGrid data
grdDefault.DataSource = dataSet;
grdDefault.DataBind();

The two important parameters of this method are as follows absoluteExpiration And slidingExpiration
absoluteExpiration  DateTime type , Represents the absolute expiration time
slidingExpiration  TimeSpan type , Represents the sliding expiration time
absoluteExpiration And slidingExpiration Can't be used at the same time
for example : Set the absoluteExpiration When parameters are ,slidingExpiration Must be set to System.Web.Caching.Cache.NoSlidingExpiration
conversely : Set the slidingExpiration When parameters are ,absoluteExpiration Must be set to System.Web.Caching.Cache.NoAbsoluteExpiration

4、 Use Insert(String, Object, CacheDependency, DateTime, TimeSpan, CacheItemPriority,

For more details, please check :http://www.111cn.net/net/net/56762.htm

CacheItemRemovedCallback) Insert Cache

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

#region Event handling
    // Page loading
    protected void Page_Load(object sender, EventArgs e)
    {
        // Cache entry removed
        if(PriorityAndCallbackDemo.CacheItemRemoved)
        {
            ltMessage.Text = string.Format("Key={0} Removed from cache , The reason is :{1}", PriorityAndCallbackDemo.CacheItemKey, PriorityAndCallbackDemo.Reason.ToString());
        }
    }

//' Add cache ' Button Click event Handle
    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"));

// Use Web.config As a cache expiration dependency
            CacheDependency dependency = new CacheDependency(this.Server.MapPath(@"Web.config"), DateTime.Now);

// Join the cache , Set the priority to the default level
            this.Cache.Insert(PriorityAndCallbackDemo.CacheItemKey, dataSet, dependency, DateTime.Now.AddMinutes(1), System.Web.Caching.Cache.NoSlidingExpiration, CacheItemPriority.Default, new CacheItemRemovedCallback(this.CacheItemRemovedHandler));
        }

// binding GridView data
        grdDefault.DataSource = dataSet;
        grdDefault.DataBind();
    }

//' Remove the cache ' Button Click event Handle
    protected void btnRemoveCache_Click(object sender, EventArgs e)
    {
        if(this.Cache[PriorityAndCallbackDemo.CacheItemKey] != null)
        {
            this.Cache.Remove(PriorityAndCallbackDemo.CacheItemKey);
        }
    }
    #endregion

#region Private method
    // Cache item removal event handling
    private void CacheItemRemovedHandler(string key, object value, CacheItemRemovedReason relason)
    {
        PriorityAndCallbackDemo.CacheItemRemoved = true;
        PriorityAndCallbackDemo.Reason = relason;
    }
    #endregion
}

The two important parameters of this method are as follows CacheItemPriority And CacheItemRemovedCallback
CacheItemPriority  Cache item priority , When the server is out of memory , The higher the priority, the less easy it is to remove
CacheItemRemovedCallback  This parameter is the delegate type , Called when the cache item is removed , contain Reason Parameter is used to indicate why the cache item is removed

【 How I use it 】

First, understand the caching strategy . Adjustable expiration policy and Absolute expiration policy . Be careful , Both cannot be used at the same time

Use an adjustable expiration policy , Need to put absoluteExpiration=DateTime.MaxValue ,TimeSpan .FromMinutes(10) Set items only in 10 It will only be removed if it is not used within minutes

The code is as follows Copy code
Cache.Insert("data", "123", null , DateTime.MaxValue, TimeSpan.FromMinutes(10));

Absolute strategy , Such as the weather report , Save the information 60 minute

The code is as follows Copy code
Cache.Insert("data", "123", null , DateTime.Now.AddMinutes(60), TimeSpan.Zero);

Cache dependency .

That is, the failure of one cache depends on another object. there object You can refer to another cache , Or a file , perhaps ....

class :CacheDependency Namespace System.Web.Caching.CacheDependency Depending on other cache items

The code is as follows Copy code
System.Web.Caching.CacheDependency cacheDependency = new System.Web.Caching.CacheDependency (null, new string [] { "time" });
Cache.Insert( "number", ++num, cacheDependency);
 
Depending on a file or folder
 
System.Web.Caching. CacheDependency cacheDependency = new System.Web.Caching.CacheDependency ( "test.xml");
When test.xml File deletion 、 Automatically remove from cache when updating
 
System.Web.Caching.CacheDependency cacheDependency = new System.Web.Caching.CacheDependency(null, new string[] { "time" });
Cache.Insert("test", "123", cacheDependency);

Remove item callback
 Cache.Insert("test", "123", null , DateTime.Now.AddSeconds(10), TimeSpan.Zero, new CacheItemUpdateCallback(Test));
 
 
 private void Test(string key, CacheItemUpdateReason reason, out object expensiveObject, out CacheDependency dependency, out DateTime absoluteExpiration, out TimeSpan slidingExpiration)
    {
 
    }

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