Namespaces

1
Namespaces

• Tonga Institute of Higher Education

2
Introduction to Namespaces

• The .Net Framework provides many classes for
  doing different things
• File Input/Output
• Displaying Windows
• Database Connectivity
• Etc.
• Microsoft needed a way to organize the classes.
  They decided to use namespaces.
• It is like the address of a class
• .NET Framework Class Library The entire
  collection of classes Microsoft made for .NET
  organized by namespaces

3
Namespace Fundamentals

• Namespaces organize the objects defined in an
  assembly
• Assemblies Primary unit of deployment for .NET
  Applications
• Dynamic Link Library (.DLL)
• Executable (.EXE)
• Assemblies can contain multiple namespaces, which
  can in turn contain other namespaces
• Namespaces prevent ambiguity and simplify
  references when using class libraries

4
Namespace Structure

• Namespaces are arranged hierarchically. Each
  namespace has a position above or below another
  namespace
• You can have namespaces inside of namespaces

System
Contains Classes
Math
Operating System
Data
Text
Decoder
StringBuilder
Encoder
DataRow
Class
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Namespace Names

• The name of a namespace is actually a list of
  names separated by periods.

System.Text
System
Math
Operating System
Data
Text
Decoder
StringBuilder
Encoder
DataRow
System.Data.DataRow
System.Text.StringBuilder
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Using Namespaces

• If you want to use a built-in .NET class, first
  look it up in the Microsoft Developer Network
  Library (MSDN)
• The MSDN Library is installed on your computer
• Start -gt Microsoft Developer Network -gt MSDN
  Library for Visual Studio .NET 2003
• You can also find it online, but this is slower
• www.msdn.com
• If you know the class you want to use, search for
  that class.
• Otherwise, search for the .NET Framework Class
  Library Reference

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Demonstration

• .NET Framework Class Library Resources

8
Imports Statements 1
System
Math
Operating System
Data
Text
Decoder
StringBuilder
Encoder
DataRow

• To use a class you must tell Visual Studio .NET
  where to find it.
• Use the fully qualified namespace (The full name)
• Dim x As System.Text.StringBuilder
• Use an imports statement
• Imports System.Text
• Dim x As StringBuilder

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Imports Statements 2

• Typing a fully qualified namespace is a lot of
  work
• The Imports statement makes this easier

The namespace that contains the class you use
Does not need to be the full name
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Demonstration

• Using Import Statements

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Import Defaults

• Visual Basic .NET automatically imports a few
  namespaces
• To see these Solution Explorer -gt Project -gt
  Right Click -gt Properties -gt Common Properties -gt
  Imports

12
Demonstration

• Import Defaults

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References

• Namespaces organize the objects defined in an
  assembly
• Assemblies Primary unit of deployment for .NET
  Applications
• There are 2 kinds
• Dynamic Link Library (.DLL)
• Executable (.EXE)
• Each project has a list of standard assemblies it
  references
• If you want to use a class inside an assembly
  that is not automatically included, you must add
  it
• To add a reference to an assembly
• Solution Explorer -gt Project Name -gt References
  -gt Right Click -gt Add Reference
• Select an assembly from the list or browse for
  the assembly

Standard assembly references
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Demonstration

• Default References and
• Adding References

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Creating a NameSpace

• If we write code and share it with others we can
  use a namespace to organize our code
• Others will import the namespace we created to
  use our code in their program

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Creating a NameSpace

• If you want to make your own namespace to be used
  in other programs, define it.
• Solution Explorer -gt Project Name -gt Right Click
  -gt Properties -gt Common Properties -gt General -gt
  Root Namespace

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Demonstration

• Creating a Namespace