The .NET Base Class Library

The .NET base class library is a collection of object-oriented types and interfaces that provide object models and services for many of the complex programming tasks we will face. Most of the types presented by the .NET base class library are fully extensible, allowing we to build types that incorporate our own functionality into our managed code. In this lesson, we are introduced to some of the .NET base class library namespaces and learn how to reference the library and use its types and methods.
The .NET Framework base class library contains the base classes that provide many of the services and objects we need when writing our applications. The class library is organized into namespaces. A namespace is a logical grouping of types that perform related functions. For example, the System.Windows.Forms namespace contains all of the types that make up windows forms and the controls used in those forms.
Namespaces are logical groupings of related classes. The namespaces in the .NET base class library are organized hierarchically. The root of the .NET Framework is the System namespace. Other namespaces can be accessed with the (period) operator. Typical namespace construction appears as follows:

System
System.Data
System.Data.SQLClient


Some Representative .NET Namespaces

Namespace Description
System:

This namespace is the root for many of the low-level types required by the .NET Framework, and is the root for primitive data types as well. This namespace is also the root for all the other namespaces in the .NET base class library.

System.Collections:

This namespace contains classes that represent a variety of different container types, such as ArrayList, SortedList, Queue, and Stack. We can also find abstract classes such as CollectionBase, which are useful for implementing our own collection functionality.

System.ComponentModel:

This namespace contains classes involved in component creation and containment, such as attributes, type converters, and license providers.

System.Data:

This namespace contains classes required for database access and manipulations, as well as additional namespaces used for data access.

System.Data.Common:

This namespace contains a set of classes that are shared by the .NET managed data providers.

System.Data.OleDb:

This namespace contains classes that make up the managed data provider for OLE DB data access.

System.Data.SqlClient:

In this namespace, we will find classes that are optimized for interacting with Microsoft SQL Server.

System.Drawing:

This namespace exposes GDI+ functionality and provides classes that facilitate graphics rendering.

System.IO

In this namespace, we will find types for handling file system IO.
System.Math This namespace is home to mathematics functions such as extracting roots, trigonometry functions, and other common mathematical functions.

System.Reflection

This namespace provides support for obtaining information and dynamic creation of types at run time.

System.Security:

This namespace is home to types dealing with permissions, cryptography, and code access security.

System.Threading

This namespace contains classes that facilitate the implementation of multithreaded applications.

System.Windows.Forms

This namespace contains types involved in creating standard windows applications. Classes that represent forms and controls reside here as well.