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This article mainly shows you "what is VB.NET Namespace", the content is easy to understand, clear, hope to help you solve your doubts, let the editor lead you to study and learn "what is VB.NET Namespace" this article.

Do you have an in-depth understanding of the objects defined by the naming organization in the assembly? Assemblies can contain multiple VB.NET namespaces, while namespaces can contain other namespaces. Namespaces avoid ambiguity when using large groups of objects, such as class libraries, and simplify references. Let's take a look at an example.

For example,. NET Framework defines the ListBox class in the System.Windows.Forms namespace. The following code snippet shows how to declare a variable using the fully qualified name of the class:

Visual Basic Dim LBox As System.Windows.Forms.ListBox

one。 Avoid name conflicts

The .NET Framework namespace solves the problem sometimes referred to as "namespace contamination", where the use of similar names in another library hampers the developer of the class library. These conflicts with existing components are sometimes referred to as "name conflicts".

For example, if you create a new class called ListBox, you can use it without any qualification within the project. However, if you want to use .NET Framework ListBox classes in the same project, you must use a fully qualified reference to make the reference *. If the reference is not * *, Visual Basic generates an error indicating that the name is ambiguous. The following code example shows how to declare these objects:

Visual Basic 'Define a new object based on your ListBox class. Dim LBC As New ListBox 'Define a new Windows.Forms ListBox control. Dim MyLB As New System.Windows.Forms.ListBox

The following figure illustrates two namespace hierarchies, both of which contain an object named ListBox.

By default, each executable created with Visual Basic contains a namespace with the same name as the project. For example, if you define an object within a project named ListBoxProject, the executable ListBoxProject.exe will contain a namespace named ListBoxProject.

Multiple assemblies can use the same namespace. Visual Basic treats them as a single set of names. For example, you can define classes for a namespace named SomeNameSpace in an assembly named Assemb1, and additional classes for the same namespace in an assembly named Assemb2.

two。 Fully qualified name

A fully qualified name is an object reference prefixed with the name of the namespace in which the object is defined. If you create a reference to this class (choose add reference on the Project menu), and then use the fully qualified name of the object in your code, you can use objects defined in other projects. The following code snippet shows how to use the fully qualified name of an object in another project namespace:

Visual Basic Dim LBC As New ListBoxProject.Form1.ListBox

Naming conflicts because they enable the compiler to determine which object is being used. However, the name itself can become tedious and tedious. To avoid this, you can use the Imports statement to define an alias, which is an abbreviated name that can be used instead of a fully qualified name. For example, the following code example creates aliases for two fully qualified names and uses these aliases to define two objects.

Visual Basic Imports LBControl = System.Windows.Forms.ListBox Imports MyListBox = ListBoxProject.Form1.ListBox Visual Basic Dim LBC As LBControl Dim MyLB As MyListBox

If you use an Imports statement instead of an alias, you can use all the names in that namespace without qualification, as long as they are * * to the project. If the Imports statement of the namespace that the project contains contains an item with the same name, you must fully qualify it when using that name. For example, suppose the project contains the following two Imports statements:

Visual Basic 'This namespace contains a class called Class1. Imports MyProj1 'This namespace also contains a class called Class1. Imports MyProj2

An error will be generated if you try to use Class1,Visual Basic without full qualification, indicating that the name Class1 is unclear.

VB.NET Namespace level statement

Within a namespace, you can define items such as modules, interfaces, classes, delegates, enumerations, structures, and other namespaces. Items such as properties, procedures, variables, and events cannot be defined at the namespace level. These items must be declared in containers such as modules, structures, or classes.

Be careful

If the namespace you define is a nested hierarchy, code in that hierarchy may be blocked when it accesses classes in other namespaces of the same name. For example, if you define a namespace called System in a namespace called SpecialSpace, members of the .NET Framework System namespace will not be accessible unless you fully qualify those members with the keyword Global.

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