Introduction
It is a way to store the frequently used data
into the server memory which can be retrieved very quickly.
Caching increase the
performance of the Web applications. Caching is a technique of persisting the
data in memory for immediate access to requesting program calls.
For example
If user is required to fetch the same data from
database frequently then the resultant data can be stored into the server memory
and later retrieved in very less time (better performance). And the same time
the application can serve more page request in the same time (scalability).
ASP.NET provides the following types of caching
that can be used to build highly responsive Web applications.
Output caching
Output caching is used for pages and is also
known as Page-level caching. All you need to do to enable output caching is to
add a directive in your html view of the aspx page. The output directive can be
written like this.
@ OutputCache Duration="60"
VaryByParam="none"
The above syntax
specifies that the page be cached for duration of 60 seconds and the value
"none" for VaryByParam attribute makes sure that there is a single cached page
available for this duration specified. VaryByParam can take various "key"
parameter names in query string.
Fragment caching
Fragment caching is used to cache portions of a
response generated by a request. Instead of caching the complete page, some
portion of the rendered html page is cached.
Example
User Control used into the page is cached and
so it doesn't get loaded every time the page is rendered.
Data caching
Data caching allows developers to
programmatically retain arbitrary data across requests. This feature is
implemented using the Cache class. Caching is one of the coolest features in
Asp.net. Caching enables you to store the expensive data into Cache object and
later retrieve it without doing expensive operations. Data Caching can
tremendously increase performance since each time the data is requested you can
turn to the Cache object rather than going to the database and fetching the
result.
Objects can be stored as name value pairs in
the cache. A string value can be inserted into the cache as follows:
Cache["name"]="Rohatash";
The stored string value can be retrieved like this.
If
Cache("name") IsNot
Nothing Then
Label1.Text = Cache("name").ToString()
End
If