Understanding the .NET Framework - The .NET Framework Class Library

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The .NET Framework class library contains a collection of programming classes that enable your applications to perform various functions. These classes are organized into related groupings referred to as Namespaces. As the name implies, all class names with a given Namespace must be unique. The .NET Framework Namespaces use a dot notation syntax scheme to describe a hierarchical organization. This naming scheme allows developers to easily group together related classes as well as to extend the functionality of a Namespace in an organized and easy-to-understand manner. Namespaces adhere to the following naming pattern: companyname.technologyname. One clear example of this is the Microsoft.Win32 Namespace, which is a Microsoft-created Namespace that contains classes that enable an application to access the Win32 API set. Another example of this naming scheme within the .NET Framework is the System.Data Namespace, which is the root level of the ADO.NET classes. Two examples of the classes that are grouped together at the next level of the System.Data class hierarchy are the System.Data.SqlClient and the System.Data.OledbClient. Each of these sets of classes are independent. No functions in the System.Data.SlqClient require the System.Data.OleDbClient, and vice versa. Further, each of these sets of classes are dependent on and subordinate to the System.Data level.

Using the different .NET Namespaces and classes in your applications is really quite easy. To use the classes contained in a given Namespace in your application, you just need to include an import directive for that Namespace. The most difficult part of using the .NET Framework class libraries is knowing which Namespace provides support for what type of functionality. By default, all .NET applications include the System Namespace, which provides basic support for variables and data types like Objects, Bytes, Int32, and Strings, as well as the Exception classes that provide structured error handling. However, to provide support for other functions, you need to include various Namespaces from the .NET Framework class libraries. Using the ADO.NET System.Data Namespace to provide database access is one of the best examples of this. In order to use ADO.NET and access databases from your .NET application, you need to include the System.Data Namespace, which enables your application to use the data access classes and methods provided by the ADO.NET technology. More detailed information about ADO.NET is presented in the next chapter of this book. Familiarizing yourself with the basic Namespaces in the .NET Framework is a vital step toward using the .NET Framework effectively and productively. The following section provides an overview of the class libraries provided with the Microsoft .NET Framework.

Microsoft Namespaces

Table 2-6 provides a brief overview of the different Microsoft Namespaces provided as a part of the .NET Framework.

Namespace	Description
Microsoft.CSharp	Contains the classes required to compile C# source code
Microsoft.JScript	Contains the classes required to support the JScript runtime
Microsoft.VisualBasic	Contains the classes required to compile Visual Basic.NET source code as well as the Visual Basic runtime
Microsoft.Vsa	Provides classes that enable you to integrate the .NET scripting interface in your applications
Microsoft.Win32	Contains the classes that enable your application to handle events that are raised by the system as well as classes that enable your application to read and write to the Registry

Table 2-6. Microsoft Namespaces in the .NET Framework Class Library

System Namespaces

Table 2-7 provides a brief overview of the different Namespaces provided by the System Namespace in the .NET Framework class library. 

Namespace	Description
System	The most fundamental of all the .NET Framework Namespaces; it must be used by all applications, and it contains the classes that represent the basic data types that were presented earlier in the "Common Type System" section.
System.CodeDom	Contains classes that are used to represent a source code document.
System.Collections	Contains classes used to manage collections of objects.
System.ComponentModel	Provides classes that control the design-time and runtime behavior of components and controls.
System.Configuration	Contains classes that enable your application to access the .NET Framework configuration settings.
System.Data	Provides support for ADO.NET and its database access classes and data types. The basic ADO.NET data management classes contained in the System.Data Namespace are the DataSet and DataTable classes that enable disconnected data access for Windows and Web-based applications. The specific System.Data classes are discussed in more detail in the next chapter.
System.Diagnostics	Contains classes that enable your application to manage system processes as well as read the system event logs and performance monitor counters.
System.DirectoryServices	Contains classes that enable your application to access the Active Directory via the ADSI(Active Directory Services Interface).
System.Drawing	Contains classes that access the system's GDI+ functions, which provide graphics support.
System.EnterpriseServices	Contains classes that provide access to COM+ for n-tiered enterprise application support.
System.Globalization	Contains classes that enable National language Support (NLS) as well as support for Calendar objects.
System.IO	Contains classes that enable your applications to read and write to data streams either synchronously or asynchronously.
System.Management	Contains classes that provide access to the WMI (Windows Management Interface) infrastructure to provide systems monitoring and management support.
System.Messaging	Contains classes that enable your application to read and write messages for the Microsoft Messaging Queuing technology.
System.Net	Contains classes that enable your application to conduct network communications using HTTP, as well as TCP and UDP sockets.
System.Reflection	Contains classes that enable the application to read the metadata of a loaded assembly.
System.Resources	Contains classes that enable your application to store and load regional-specific resources.
System.Runtime.ComplierServices	Contains classes that allow compiler developers to control aspects of the runtime behavior of the CLR.
System.Runtime.InteropServices	Contains classes that enable your .NET applications to interface with COM (Component Object Model) objects and native Win32 APIs (Application Program Interfaces).
System.Runtime.Remoting	Contains classes that enable your application to manage remote objects required for developing distributed applications.
System.Runtime.Serialization	Contains classes that allow your applications to store and load objects by converting them into a sequential stream of bytes (serialization).
System.Security	Contains classes that enable your application to control .NET Framework security features. These classes can manage security features such as permissions, policies, and cryptography.
System.ServiceProcess	Contains classes that allow your applications to create, install, and manage Windows services.
System.Text	Contains classes that represent ASCII,  Unicode, UTF-7, and UTF-8 character sets.
System.Threading	Contains classes that enable you to develop multithreaded applications.
System.Timers	Contains classes that permit your application to raise an event following a specified interval of time.
System.Web	Contains a set of classes that define ASP.NET. These classes essentially provide support for Web browser to Web server interaction. For example, different classes contained in this Namespace support Web hosting, mail, security, and user interface components.
System.Windows.Forms	Contains the classes that enable the development of Windows-based applications.
System.Xml	Contains a set of classes that enable your application to work with XML documents.

Table 2-7. System Namespaces in the .NET Framework Class Library

This is chapter two of ADO.NET: The Complete Reference, by Michael and Denielle Otey (McGraw-Hill/Osborne, ISBN 0-07-222898-9, 2003). Check it out at your favorite bookstore today. Buy this book now.

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