The Enterprise Library consists of the following seven Application Blocks. 

·         Data Access Application Block

·         Exception Handling Application Block

·         Logging and Instrumentation Application Block

·         Security Application Block

·         Cryptography Application Block

·         Caching Application Block

·         Configuration Management Application Block

The following sections discusses each of these blocks briefly.

Data Access Application Block

The Data Access Application is one of the most popular of the Enterprise Library Application blocks and has been widely used in enterprise applications.  The earlier versions of this block contained static methods that could have posed problems due to thread safety issues in multithreaded scenarios.  The newer version, however, makes use of the Abstract Factory pattern to solve all these issues.  The salient features of the Data Access Application Block include:

·         Support for both SQL Server and Oracle databases

·         Extensible

·         Tightly coupled with the Configuration Management Block

Exception Handling Application Block

An exception is an error that occurs at runtime.  If the same is not handled by your code, it might lead to premature termination of the flow of execution of your application.  Exceptions should be handled very carefully as handling them are quite expensive and too many exception blocks in your code might lead to poor application performance.  The Patterns and Practices group from Microsoft has introduced the Exception Handling Application Block with the sole purpose of providing the application developers with a set of the best practices and strategies that should be followed for handling exceptions in the code.  The salient features of the Exception Handling Application Block include:

·         Encapsulates the recommended best practices on handling exceptions

·         Support for logging exceptions

·         Extensibility

·         Ease of use

Logging and Instrumentation Application Block

Efficient Logging and Instrumentation feature in an enterprise application development phase facilitates application performance monitoring.  Hence, it is a very important feature in enterprise application software development.  The Patterns and Practices group from Microsoft has come up with this powerful block that can be instrumental in the above stated situations.  The salient features of the Logging and Instrumentation Application Block include:

·         Support for logging synchronously and asynchronously

·         Support for formatters

·         Support for logging to different destinations

Security Application Block

The Security Application Block from the Patterns and Practices group of Microsoft facilitates the implementation of security features in enterprise applications built on top of the Microsoft .NET framework.  The salient features of the Security Application Block include:

·         Support for authentication and authorization

·         Supports both role and profile management

·         Plug ability with the Data Access Application Block

·         Plug ability with the Cryptography Application Block

Cryptography Application Block

The Cryptography Application Block is a collection of reusable and extensible code that simplifies the usage of cryptographic functionality in applications that are designed on the Microsoft.NET framework.  The salient features of the Cryptography Application Block include:

·         Plug ability

·         Configurable

·         Extensible

Caching Application Block

Caching is an important feature that promotes improvement of application performance by storing the frequently used pages or data in main memory.  The Caching Application Block from the Patterns and Practices group of Microsoft encapsulates efficient, consistent caching strategies and, hence, simplifies implementation of caching strategies in enterprise application development. The salient features of the Caching Application Block include:

·         Support for efficient caching strategies in web applications

·         Configurable

·         Thread Safety

Configuration Management Application Block

The Configuration Management Application Block from the Patterns and Practices group of Microsoft provides, "a seamless integration with configuration sources other than XML files.  You could use the registry, a database, or many other storage mediums, all using a common interface to manipulate the configuration information."  The salient features of the Configuration Management Application Block include:

·         Support for reading and writing the configuration data

·         Support for storing configuration data at multiple locations

·         Support for caching the configuration data

·         Plug ability