Why need to
cache data in ASP.Net?
Most of the developers don’t know where can use cache
mechanisam in ASP.Net. For good
performance of ASP.Net dynamic application we can use cache mechanism. This is
nothing but we store some dynamic data into the cache for reusablility of web
pages when user request the same again. That means suppose we have a link in
our websites, that displays all the items in the database. When user clicks
first time, it will fetch all data from the database and displayed to the web
page. If a user trying to get same data for the second time, normally we are
not able track whether the user tried same data before, so we are doing same
procedure again (Fetching data from database and render to the html). As a
optimisation part of the we bsite, we need to fetch same data only in single
time for a user (Because new items inserted in to the database is rare case).
Simple
codes to cache data in ASP.Net
To achieve tracking of user’s request, we can use cache
mechanism. In the above example when a user trying to get all items from the
database, we need to fetch this data and will store to cache object. When the
same user trying to get same data for the second time, we need to check is
there any data in the cache object, if it is there just displayed to the web
page else taken from the db and store to the cache for future.
How to
store a string variable to cache?
Cache["name"]="Smitha";
if (Cache["name"] != null)
Label1.Text=
Cache["name"].ToString();
To insert objects into the cache, the Add
method or different versions of the Insert method of the Cache class can be
used. These methods allow us to use the more powerful features provided by the
Cache class. One of the overloads of the Insert method is used as follows: (How
to store data object into cache in ASP.Net ?)
Cache.Insert("Name", strName,
new
CacheDependency(Server.MapPath("name.txt"),
DateTime.Now.AddMinutes(2), TimeSpan.Zero);
The first two parameters are the key and the
object to be inserted. The third parameter is of type CacheDependency and helps
us set a dependency of this value to the file named name.txt. So whenever this
file changes, the value in the cache is removed. We can specify null to
indicate no dependency. The fourth parameter specifies the time at which the
value should be removed from cache. [See example 5 for an illustration.] The
last parameter is the sliding expiration parameter which shows the time
interval after which the item is to be removed from the cache after its last
accessed time.
The cache automatically removes the least used
items from memory, when system memory becomes low. This process is called
scavenging. We can specify priority values for items we add to the cache so
that some items are given more priority than others:
Cache.Insert("Name", strName,
new
CacheDependency(Server.MapPath("name.txt"),
DateTime.Now.AddMinutes(2), TimeSpan.Zero,
CacheItemPriority.High, null);
