ASP.NET has built-in cache engine that is used by ASP.NET pages to store and retrieve objects across HTTP
The ASP.NET cache is private to each application and stores objects in memory.
The lifetime of the cache is equivalent to the lifetime of the application;
that is, when the application is restarted, the cache is recreated.
Placing an item in the
cache is done in following way:
Cache ("key") = Value
Retrieving the data is just as simple
Value = Cache("key")
If Value <> Null Then
For sophisticated functionality in
Applications on ASP.NET cache supports scavenging, expiration, and file and key
- Scavenging means that
the cache attempts to remove infrequently used or unimportant items if memory
- Expiration allows
programmers to give cache items lifetimes, which can be explicit (for example,
expire at 12:00) or can be relative to an item's last use (for example, expire
10 minutes after the item was last accessed). After an item has expired, it is
removed from the cache and future attempts to retrieve it return the null value
unless the item is reinserted into the cache.
- File and key
dependencies allow the validity of a cache item to be based on an external file
or on another cache item. If a dependency changes, the cache item is
invalidated and removed from the cache. For an example of how you might use
this functionality, consider the following scenario: an application reads
financial information from an XML file that is periodically updated. The
application processes the data in the file and creates a graph of objects that
represent that data in a consumable format. The application caches that data
and inserts a dependency on the file from which the data was read. When the
file is updated, the data is removed from the cache and the application can
reread it and reinsert the updated copy of the data.
Data Caching example
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<script language="VB" runat="server">
Sub Page_Load(Src As Object, E As EventArgs)
Dim dataSource As DataView
dataSource = Cache("CheDataSet")
If dataSource Is Nothing
Dim Conn As SqlConnection
Dim Cmd As SqlDataAdapter
Conn = New SqlConnection(_
Cmd = New SqlDataAdapter("select * from customers", Conn)
Dim ds As New DataSet
dataSource = New DataView(ds.Tables("dsUsers"))
Cache("CheDataSet") = dataSource
CacheMsg.Text = "Dataset was Created directly from the Datebase. " &_
"Here the Cache was not used but the Cache was " &_
"Created, so check for the performance next time."
cacheMsg.Text = "Dataset was Retrieved from cache which was " &_
1. When Executed for the first time
2. When Executed after the cache is created.
- Data Caching should be
used very carefully only when required.
- Data caching allows
objects to be cached programmatically.
- The cache is scoped to
an application and its lifetime is equivalent to the lifetime of the