Most of us might have heard about Enterprise library. We even used in our code also. In this series of articles, I am going to explain about Enterprise library and its application blocks in brief. We will start with introduction to Enterprise library and benefits of using it. In this series, I am going to use Enterprise Library 4.1. It's a free download and available at Here.  Microsoft Patterns & Practices team will be taking care of Enterprise library design.

What is Enterprise Library?

Enterprise library is a set of application blocks and services that will make our coding work easier. Application blocks are nothing but reusable software components, which can be plug-in into the projects for solving commonly occurring problems. It provides a high level of abstraction over existing class libraries.

Benefits of using Enterprise Library:

1. Consistency: By using it, we can make sure that code written for a particular task like caching or exception handling will be consistent across all developers and projects.
2. Time Saving: By using it, we can handle most of the common tasks of a project with minimal lines of code and configuration settings, which will save time in turn.
3. Reduced Errors: We can reduce errors count by using it.
4. Extensibility: We can extend any of the application blocks as per our requirements.
5. Easy Integration: All application blocks are based on plug-in pattern. So, we can easily integrate it into our code.
6. Additional Functionality: By using it, sometimes we can get extra functionality which is not provided by base libraries.

Based on the functionality provided, application blocks are classified as:

Types of Application Blocks:

1. Caching Application block: This can be used to handle tasks related to caching of data. It provides all functionality required for storing and retrieving data from cache either from in-memory or database.
2. Cryptography Application block: This can be used to incorporate security for the data with cryptographic algorithms and classes. It frees developers from understanding complex classes for implementing security.
3. Data Access Application block: This will provide classes based on ADO.NET for accessing external data easily with minimal lines of code. It is one of the blocks, which got high popularity. 
4. Exception Handling Application block: It provides a consistent way of handling exceptions in all the layers of our code. 
5. Logging Application block: This will help to log all kind of messages easily either in event log or external database. It provides a single interface by which we can log messages in any storage media without changing code.
6. Policy Injection Application block:  It provides a mechanism for applying policies to objects. We will define set of policies for the target classes and their members through configuration of the Policy Injection Application Block or by applying attributes to individual members of the target class.
7. Security Application block: It helps to implement authorization and authentication mechanisms into the system easily.
8. Unity Application block: It provides constructor, property, and method call injection. We will look into this in depth in coming articles.
9. Validation Application block: It provides simple and easy way of implementing validations.

Based on our requirement, we can use that application block only. Dependencies among application blocks got reduced a lot in the release of 3.0 and 4.0 versions.

Configuration block is the base for customizing any of the above application blocks.

History of Enterprise Library:

Now, we will have a small look into the past versions of Enterprise Library and its contents: 

• First release of Enterprise Library is in 2005 targeting 1.1 Framework. This has been deprecated.
   
• Second release (version 2.0) was in 2006 targeting both 1.1 & 2.0 Frameworks.

  This release is having following application blocks:

  1. Caching Application Block
  2. Cryptography Application Block
  3. Data Access Application Block
  4. Exception Handling Application Block
  5. Logging Application Block
  6. Security Application Block
      

• Third release (3.1) was in 2007 targeting 2.0 and 3.0 frameworks. It had enhancements to existing blocks and additional ones apart from above.
  
  Additional blocks in this release are:
   

  1. Policy Injection Application Block

  2. Validation Application Block
      

• Fourth release (4.0) was in 2008. It is targeting 3.5 framework. It is having Unity Application Block as a new entry.
   

• Fifth and latest release was in Oct 2008. It is targeting 3.5 framework. It does not have any new blocks. But having enhancements to existing blocks and performance improvements.

I will end up the things here. In coming articles, we will go deep into Application blocks. I hope this article will be helpful for all.