Data Caching using Enterprise Library

Introduction

Caching is one of most important factors if we think about application performance. Most applications need a caching implementation to improve performance. The Caching Application Block provides a flexible and extensible caching framework with a set of APIs that can be used at any layer of an application. It supports in-memory, database, or isolated storage for storing cached data. We can use it in web applications as well as Windows applications. Implementing caching using the Caching Application Block improves the performance of applications as well as reduces development time and cost. This application block provides all kinds of functions like adding, removing, and managing the expiration of cache. In this article, I have explained how we can use the Caching Application Block of Enterprise Library 4.1 in an ASP.NET Web application. But as I said earlier, the Caching Application Block is very generic and can be used in different applications without changing a single line of code. In other words, we can say the Enterprise Library Caching Application Block provides a ready to use caching framework. Hope this article will help all of you. Please provide your valuable suggestions and feedback to improve my article.

Where can the Caching Application Block be used?

The Enterprise Library Caching Application Block is a ready to use caching framework that can be used in various applications like:

• ASP.NET Web applications
• Windows Forms
• Console
• Windows Service
• Enterprise Services
• Web Service

This caching application block has in-built features like inserting an item into cache, remove from cache, cache expiration settings, etc. This is extensible as well as per your requirement.

Installing Enterprise Library 4.1

First of all, we need to install Enterprise Library before we start working with any of the application blocks. As of now, the latest version of Enterprise Library is 4.1. This article is based on the same version. You can download and install Enterprise Library easily from Enterprise Library 4.1-October 2008.
Microsoft Enterprise Library is a collection of reusable application blocks designed to assist software developers with common enterprise development challenges. This release includes caching, cryptography, data access, exception handling, logging, policy injection, security, validation, and unity.

Using Enterprise Library Configuration Manager

Enterprise Library's API is based on an XML configuration. The application configuration file contains all related information regarding application blocks. As this is an XML configuration, we can do all kinds of manual changes in the file but it’s quite difficult to remember all the configuration and properties. Microsoft provides the Enterprise configuration UI console to configure the application block using a UI.
After installing Enterprise Library 4.1, you can find the Enterprise Library Configuration Manager in the Bin directory of your installed location. In my case, it is in "C:\Program Files (x86)\Microsoft Enterprise Library 4.1 - October 2008\Bin". Run EntLibConfig.exe. Or you can go to Start > Select Program Files > Microsoft Patterns and Practices > Enterprise Library >Enterprise Library Configuration. The following screen will appear:

Configure Caching Application Block

Now click on File > Open application. Select the "web.config" of your ASP.NET web application.

By default, Enterprise Library configuration has a Data Access Application Block setting added. We can easily remove any configuration settings by using right click > Remove.
Now we can add a "Caching Application Block" using right click on Root > New > Caching Application Block.

A new configuration section "Caching Application Block" will be automatically added with the configuration File.



Save the configuration in Configuration Manager. Now open the web application and check the web.config file for changes. You will find the below Config section has been added in the web.config file after adding the Caching Application Block using the Enterprise Application Manager.

Using the Caching Application Block

Adding Reference

As the caching application block is a predefined set of code and is defined in a framework, we need to add some reference to our application. These are Microsoft.Practices.EnterpriseLibrary.Caching.dll and Microsoft.Practices.EnterpriseLibrary.common.dll. These two are sufficient for using the Caching Application Block.



After adding a reference, we have to add a namespace for using the Caching Application Block. These are:

using Microsoft.Practices.EnterpriseLibrary.Caching;
using Microsoft.Practices.EnterpriseLibrary.Common;

This is all about adding references and namespaces. Now let’s have a look at how we can do all kinds of caching operations like insert data into cache, remove from cache, display data from cache, cache expiration, etc.

Before doing any kind of caching operation, we need to initialize the CacheManager object.

Initialize Cache Manager

ICacheManager is the main interface between our application and the Caching Application Block. To create an instance of a CacheManager object, the application uses the CacheFactory class, which in turn uses the CacheManagerFactory class. The CacheManagerFactory class creates all the internal classes needed to implement a CacheManager object.

Insert Item to Cache

Now we have an instance of CacheManager. The CacheManager provides an Add() method to add a new CacheItem to the cache. By default, it takes two arguments: String Key and Object Value.
Below is a sample code snippet to show how to add a CacheItem to the cache:

Remove Item from Cache

Removing an item from cache is very easy to implement. CacheManager provides a Remove() method to remove a CacheItem from cache. This method has no overloaded method and takes only a single argument Key. If the key exists, the CacheItem will be removed automatically from CacheItems, otherwise this method will do nothing.

Retrieve Item From Cache

After adding an element into a cache, the next thing we need to do is to retrieve the cache element from the cache collection. But when retrieving the cache element, we have to make sure we are type casting the object in proper type. For example, if we have stored a DataSet as an object in cache, during retrieval, we have to make sure we are doing the same type casting.

Remove All Items From Cache

We can remove all items from cache using the Flush() method of CacheManager.

Caching Expiration

Microsoft Caching Application Block provides great use of the caching expiration functionality. For that, we need to add the namespace below:

using Microsoft.Practices.EnterpriseLibrary.Caching.Expirations;

Adding the namespace will provide us the below classes to implement the expiration of caching using the Application Block.

• AbsoluteTime
• ExtendedFormat
• ExtendedFormatTime
• FileDependency
• NeverExpired
• SlidingTime




AbsoluteTime

Absolute time defines the lifetime of a cache item by specifying the absolute time for an item to expire from the cache item collection. Absolute expirations are specified in full-time format (hh:mm:ss). The object will expire from the cache at the specified time:

ExtendedFormat and ExtendFormatTime are quite similar with AbsoluteTime configuration. I am not going into details on these two. Let us start with FileDependency.

FileDependency

File-based dependency invalidates a particular cache item when a file(s) on the disk changes. This is quite helpful when we want to update cache data if there are some changes in files or database.

NeverExpired

If we set the caching expiring policy as never expire, then data will be stored in the cache collection unless and until we use CacheManager.Remove() to remove the cache item. When we use the CacheManager.Add() method with only a key and value argument, the cache object is set to never expire mode.

Sliding

Sliding resets the time for the item in the cache to expire on each request. This is useful when an item in the cache is to be kept alive as long as requests for that item are coming in from various clients. This means the item expires after the specified time has elapsed from when the item was last accessed. The default time is 2 minutes.