Microsoft Enterprise Library is a collection of application blocks designed to assist developers with common enterprise development challenges. Application blocks are a type of guidance, provided as source code that can be used "as is," extended, or modified by developers for use in enterprise development projects. It is available for download here.
Microsoft Enterprise Library 5.0 contains the following application blocks:
Enterprise Library also includes a set of core functions, including configuration and instrumentation, and object lifecycle management. These functions are used by all other application blocks.