Use of ASP. NET Cache Cache

The ASP. NET Cache is an important way to improve system performance by using the "most recently used" principle (a least-recently-used algorithm). Caches are often used to store database data in database access .

1. Add the cache:

The addition of the cache is either add () or Insert(), and the two methods are almost similar, except that the Inser method can use the optional parameters, that is, to implement the cache additions using the default parameters:

Cache.Add (

keyname,// Cache Name

keyvalue,// the object to cache

dependencies,// Dependent Items

absoluteexpiration,// Absolute Expiration Time

slidingexpiration,// Relative Expiration Time

priority,// Priority Level

cacheitemremovedcallback);// cache expiration raises an event

2. cache dependencies:

cache can be set by the timeliness of file dependencies, other cache dependencies, database dependencies, and expiration time methods are set when the file changes, depending on the cache entry changes, when the database changes or when the time expires, the cache is invalidated, and a certain event can be raised.

2.1 file dependencies:

CacheDependency filedepends = new CacheDependency (Server.MapPath ("Northwind.xml"));

Cache.Insert ("Gridviewdataset", Dsgrid, Filedepends);

This example is used to rely on a cache using the Northiwind.xml file:

2.2 Other cache entry dependencies:

String[] Filedependsarray = {Server.MapPath ("Northwind.xml")};

String[] Cachedependsarray = {"Depend0", "Depend1", "Depend2"};

CacheDependency cachedepends = new CacheDependency (Filedependsarray, Cachedependsarray);

Cache.Insert ("Gridviewdataset", Dsgrid, Cachedepends);

This example sets the Northwind.xml file dependency and the Depend0,depend1,depend2 cache entry

Where Depend0,depend1,depend2 is an additional three caches.

If you do not need file dependencies, you can set to null.

2.3 Expiration Time Setting:

absoluteexpiration can set the absolute expiration time of the cache, such as:

Cache.Insert ("Gridviewdataset", Dsgrid, NULL, DateTime.Now.AddMinutes (+), cache.noslidingexpiration);

The cache expires 30 minutes after it is added.

noslidingexpiration can set the relative expiration time, if the cache is not accessed within the Noslidingexpiration set time, the cache expires, and if there is access during that time, the cache expiration time will be reset to the original value. such as Noslidingexpiration=20

In 20 minutes if not accessed, the cache expires, and if the cache is accessed every 19 minutes, the cache will never expire.

Cache.Insert ("Datagriddataset", Dsgrid, Null,cache.noabsoluteexpiration, Timespan.fromseconds (30));

3. Priority level:

Priority attribute value and meaning:

Priority value	Description
Notremovable	Items with this priority won't be evicted.
High	Items with this priority level is the least likely to be evicted.
AboveNormal	Items with this priority level is less likely to is evicted than items assigned Normal priority.
Default	This is equivalent to Normal.
Normal	The default value.
BelowNormal	Items with the This priority level is more likely to is evicted than items assigned Normal priority.
Low	Items with this priority level is the most likely to be evicted.

4. Cache Failure Event handling:

Using System;

Using System.Data;

Using System.Configuration;

Using System.Web;

Using System.Web.Security;

Using System.Web.UI;

Using System.Web.UI.WebControls;

Using System.Web.UI.WebControls.WebParts;

Using System.Web.UI.HtmlControls;

Using System.Web.Caching; necessary for CacheDependency

Using System.Xml; necessary for XML stuff

public partial class _default:system.web.ui.page

{

public static CacheItemRemovedCallback onremove = null;

protected void Page_Load (object sender, EventArgs e)

{

Creategridview ();

}

private void Creategridview ()

{

DataSet Dsgrid;

Dsgrid = (DataSet) cache["Gridviewdataset"];

OnRemove = new CacheItemRemovedCallback (this. RemovedCallback);

if (Dsgrid = = null)

{

Dsgrid = GetDataSet ();

String[] Filedependsarray = {Server.MapPath ("Northwind.xml")};

String[] Cachedependsarray = {"Depend0", "Depend1", "Depend2"};

CacheDependency cachedepends = new CacheDependency

(Filedependsarray, Cachedependsarray);

Cache.Insert ("Gridviewdataset", Dsgrid, Cachedepends,

DateTime.Now.AddSeconds (10),

Cache.noslidingexpiration,

Cacheitempriority.default,

OnRemove);

Lblmessage.text = "Data from XML file.";

}

Else

{

Lblmessage.text = "Data from cache.";

}

Gv. DataSource = Dsgrid.tables[0];

Gv. DataBind ();

}

Private DataSet GetDataSet ()

{

DataSet Dsdata = new DataSet ();

XmlDataDocument doc = new XmlDataDocument ();

Doc. DataSet.ReadXML (Server.MapPath ("Northwind.xml"));

Dsdata = doc. DataSet;

return dsdata;

}

public void RemovedCallback (string CacheKey,

Object CacheObject,

CacheItemRemovedReason reasontoremove)

{

WriteFile ("Cache removed for following reason:" +

Reasontoremove.tostring ());

}

private void WriteFile (string strText)

{

System.IO.StreamWriter writer = new System.IO.StreamWriter (

@ "C:" Test.txt ", true);

String str;

str = DateTime.Now.ToString () + "" + strText;

Writer. WriteLine (str);

Writer. Close ();

}

protected void Btnclear_click (object sender, EventArgs e)

{

Cache.remove ("Gridviewdataset");

Creategridview ();

}

protected void Btninit_click (object sender, EventArgs e)

{

Initialize caches to depend on.

cache["Depend0"] = "This is the first dependency.";

cache["Depend1"] = "This is the 2nd dependency.";

cache["Depend2"] = "This is the 3rd dependency.";

}

protected void Btnkey0_click (object sender, EventArgs e)

{

cache["Depend0"] = "This is a changed first dependency.";

}

}

Table 17-5. Members of the CacheItemRemovedReason enumeration
Reason	Description
Dependencychanged	A file or Item key dependency has changed.
Expired	The cached item has expired.
Removed	The cached item has been explicitly removed by the Remove method or replaced by another item with the same key.
Underused	The cached item is removed to free up system memory.

Source: http://www.cnblogs.com/leochu2008/articles/1161772.html

Use of ASP. NET Cache Cache