.NET Framework 3.0 Class Library 

The .NET Framework class library provides access to system functionality and is designed to be the foundation on which .NET Framework applications, components, and controls are built. The following sections describe many of the namespaces provided in the .NET Framework class library. To browse the entire .NET Framework 3.0 class library, see Class Library.

Fundamental Programming Namespaces

  • System – contains classes and base classes that define commonly used value and reference data types, events and event handlers, interfaces, attributes, and processing exceptions. Other classes provide services supporting data type conversion, method parameter manipulation, mathematics, remote and local program invocation, application environment management, and supervision of managed and unmanaged applications.

  • System.Collections – contains interfaces and classes that define various collections of objects, such as lists, queues, arrays, hashtables, and dictionaries.

  • System.Collections.Generic – contains interfaces and classes that define generic collections, which allow users to create strongly typed collections that provide better type safety and performance than non-generic strongly typed collections.

  • System.IO – contains types that allow synchronous and asynchronous reading and writing on data streams and files.

  • System.Text – contains classes representing ASCII, Unicode, UTF-7, and UTF-8 character encodings; abstract base classes for converting blocks of characters to and from blocks of bytes; and a helper class that manipulates and formats String objects without creating intermediate instances of String.

  • System.Threading – provides classes and interfaces that enable multithreaded programming. This namespace includes a ThreadPool class that manages groups of threads, a Timer class that enables a delegate to be called after a specified amount of time, and a Mutex class for synchronizing mutually exclusive threads.

Configuration Namespaces

Data and XML Namespaces

  • System.Data – consists of the classes that constitute the ADO.NET architecture, which is the primary data access method for managed applications.

  • System.Data.Common – contains classes shared by the .NET Framework data providers. Data providers describe a collection of classes used to access a data source, such as a database, in the managed space.

  • System.Xml – contains classes that provide standards-based support for processing XML.

Globalization and Localization Namespaces

  • System.Globalization – contains classes that define culture-related information, including the language, the country/region, the calendars in use, the format patterns for dates, currency and numbers, and the sort order for strings.

  • System.Resources – provides classes and interfaces that allow developers to create, store, and manage various culture-specific resources used in an application.

  • System.Text – contains classes representing ASCII, Unicode, UTF-7, and UTF-8 character encoding.

Interop Namespaces

  • System.Runtime.InteropServices – provides a wide variety of members that support COM interop and platform invoke services.

  • System.Runtime.InteropServices.ComTypes – contains methods that are definitions of COM functions for managed code. These functions replace the now-obsolete UCOM* methods in the System.Runtime.InteropServices namespace.

Networking Namespaces

  • System.Net – contains classes that provides a simple interface to many network protocols.

  • System.Net.Mail – contains classes used to send electronic mail to a Simple Mail Transfer Protocol (SMTP) server for delivery.

  • System.Net.NetworkInformation – provides access to network traffic data, network address information, and notification of address changes for the local computer.

  • System.Net.Sockets – provides a managed implementation of the Windows Sockets (Winsock) interface for developers who need to help control access to the network.

Reflection Namespaces

System.Reflection – contains classes and interfaces that provide a managed view of loaded types, methods, and fields, with the ability to dynamically create and invoke types.

Security Namespaces

  • System.Security – provides the underlying structure of the common language runtime security system, including base classes for permissions.

  • System.Web.Security – contains classes that are used to implement ASP.NET security in Web applications.

Serialization Namespaces

  • System.Runtime.Serialization – contains classes that can be used for serializing and deserializing objects. Serialization is the process of converting an object or a graph of objects into a linear sequence of bytes for either storage or transmission to another location. Deserialization is the process of taking in stored information and recreating objects from it.

Service Namespaces

The namespaces in the .NET Framework for interacting with a variety of back-end server resources include the following:

  • System.Diagnostics – consists of classes that allow you to debug your application and to trace the execution of your code. System.Diagnostics also provides classes that allow you to start system processes, read and write to event logs, and monitor system performance using performance counters.

  • System.DirectoryServices – consists of classes that provide easy access to the Active Directory from managed code.

  • System.IO – provides classes that listen to the file system change notifications and raises events when a directory, or file in a directory, changes.

  • System.Management – provides classes for managing information and events about the system, devices, and applications instrumented to the Windows Management Instrumentation (WMI) infrastructure.

  • System.Messaging – provides classes that allow you to connect to message queues on the network, send messages to queues, and receive or peek (read without removing) messages from queues.

  • System.ServiceProcess – provides classes that allow you to install and run services, long-running executables that run without a user interface.

  • System.Timers – provides the server-based Timer component, which allows you to raise an event on a specified interval.


    There is also a Timer control for Windows Forms in the System.Windows.Forms namespace and a Timer class in the System.Threading namespace.

See Also


ASP.NET Class Library
Windows Forms Class Library

Other Resources

.NET Framework Technologies
Windows Presentation Foundation Class Library