The MyBase Keyword Nested Classes Destructors
2.14.9 The MyBase Keyword
The MyBase keyword is used to access methods on the base class. This feature is commonly used when an overriding method needs to call the base-class implementation of the same method: Public Class BaseClass Public Overridable Sub DoSomething ... 83 End Sub End Class Public Class DerivedClass Inherits BaseClass Public Overrides Sub DoSomething Start by calling the base-class implemenation of DoSomething. MyBase.DoSomething Then continue on with additional stuff required by DerivedClass. ... End Sub End Class2.14.10 Nested Classes
Class definitions can be nested. The nested class is considered a member of the enclosing class. As with other members, dot notation is used for accessing the inner class definition. Consider this nested class definition: Public Class OuterClass Public Class InnerClass Public Sub SomeMethod Console.WriteLineHello from InnerClass.SomeMethod End Sub End Class End Class Instantiating an object of type InnerClass requires qualifying the name with the name of the enclosing class: Dim x As New OuterClass.InnerClass x.SomeMethod The accessibility of the inner-class declaration can be controlled with the class declarations access modifier. For example, in the following definition, InnerClass has been declared with the Private modifier, making it visible only within the confines of the OuterClass class: Public Class OuterClass Private Class InnerClass ... End Class End Class Classes can be nested as deeply as desired.2.14.11 Destructors
Just as constructors are methods that run when objects are instantiated, it is often convenient to define methods that run when objects are destroyed that is, when the memory that was allocated to them is returned to the pool of free memory. Such a method is called a destructor. Visual Basic .NET doesnt have special syntax for declaring destructors, as it does for constructors. Instead, Visual Basic .NET uses the specially named methods Finalize and Dispose to perform the work normally associated with destructors. Because this mechanism is actually part of the .NET Framework rather than Visual Basic .NET, it is explained in Chapt er 3 , under Memory Management and Garbage Collection. 842.14.12 Early Versus Late Binding
Parts
» VB.NET - (O'Reilly) Programming Visual Basic NET
» What Is the Microsoft .NET Framework?
» hello, world An Example Visual Basic .NET Program
» Hello, Windows An Example Visual Basic .NET Program
» Hello, Browser An Example Visual Basic .NET Program
» Source Files Identifiers The Visual Basic .NET Language
» Numeric Literals String Literals Character Literals
» Date Literals Boolean Literals Nothing Summary of Literal Formats
» Custom Types Collections Types
» The Namespace Statement The Imports Statement
» Symbolic Constants Scope The Visual Basic .NET Language
» Access Modifiers Assignment The Visual Basic .NET Language
» Unary Operators Arithmetic Operators
» Relational Operators Operators and Expressions
» String-Concatenation Operators Bitwise Operators
» Logical Operators Operator Precedence
» Call Exit Branching Statements
» Goto If RaiseEvent Branching Statements
» Return Select Case Branching Statements
» For Each Iteration Statements
» Object Instantiation and New Constructors
» Handling Events Inheritance Classes
» Passing arrays as parameters
» Variable-length parameter lists Main method
» Implementing interface methods Overriding inherited methods
» Overloading Overloading inherited methods
» The MyBase Keyword Nested Classes Destructors
» Interfaces The Visual Basic .NET Language
» Enumerations The Visual Basic .NET Language
» Exceptions The Visual Basic .NET Language
» Delegates The Visual Basic .NET Language
» Using Events and Delegates Together
» Creating Custom Attributes Attributes
» Standard Modules Conditional Compilation
» Summary The Visual Basic .NET Language
» Common Language Infrastructure CLI and Common Language Runtime CLR
» Global Assembly Cache GAC Comparison of Assemblies, Modules, and Namespaces
» Application Domains Common Language Specification CLS
» Intermediate Language IL and Just-In-Time JIT Compilation Metadata
» Finalize Memory Management and Garbage Collection
» Dispose Memory Management and Garbage Collection
» A Brief Tour of the .NET Framework Namespaces
» Configuration File Format Configuration
» Configuration Section Groups The appSettings Section
» Adding event handlers Creating a Form in Code
» Handling Form Events Windows Forms I: Developing Desktop Applications
» Relationships Between Forms Windows Forms I: Developing Desktop Applications
» Merging Menus MDI Applications
» Detecting MDI Child Window Activation
» Component Attributes Windows Forms I: Developing Desktop Applications
» The Graphics Class 2-D Graphics Programming with GDI+
» The Pen Class 2-D Graphics Programming with GDI+
» The Brush Class 2-D Graphics Programming with GDI+
» System colors The Color Structure
» Alpha Blending 2-D Graphics Programming with GDI+
» Antialiasing 2-D Graphics Programming with GDI+
» The PrintPageEventArgs Class Printing
» The OnBeginPrint and OnEndPrint Methods Choosing a Printer
» The PageSettings Class Printing
» The PrinterSettings Class Printing
» Page Setup Dialog Box Print Preview
» Summary Windows Forms I: Developing Desktop Applications
» The Button Class The CheckBox Class The ComboBox Class
» The DateTimePicker Class The GroupBox Class The ImageList Class
» The Label Class The LinkLabel Class
» The ListBox Class Common Controls and Components
» The ListBox.ObjectCollection Class
» The ListView Class Common Controls and Components
» The MonthCalendar Class Common Controls and Components
» The Panel Class The PictureBox Class
» The RadioButton Class Common Controls and Components
» The TextBox Class The Timer Class
» Other Controls and Components
» Control Events Windows Forms II: Controls, Common Dialog Boxes, and Menus
» The Anchor Property Form and Control Layout
» Controlling dock order The Dock Property
» The Splitter control The Dock Property
» ColorDialog FontDialog OpenFileDialog Common Dialog Boxes
» PageSetupDialog PrintDialog PrintPreviewDialog SaveFileDialog
» Adding Menus in the Visual Studio .NET Windows Forms Designer
» Programmatically Creating Menus Menus
» Building Controls from Other Controls
» Building Controls That Draw Themselves Building Nonrectangular Controls
» Summary Windows Forms II: Controls, Common Dialog Boxes, and Menus
» Setting control properties using attributes Adding event handlers
» AutoEventWireup Handling Page Events
» The Button control Web Controls
» The CheckBox control The DropDownList control
» The Image control The Label control
» The ListBox control Web Controls
» The RadioButton control Web Controls
» The Table control Web Controls
» The TextBox control Web Controls
» Other web controls Web Controls
» HTML Controls Handling Control Events
» Programmatically Instantiating Controls More About Server Controls
» More About Validation-Control Tag Attributes
» Using Validation-Control Properties Providing a Summary View of Validation Failures
» Performing Custom Validation Adding Validation
» Using Directives to Modify Web Page Compilation
» The Server Object ASP.NET Objects: Interacting with the Framework
» The Application Object The Session Object The Cache Object The Request Object
» The Response Object ASP.NET Objects: Interacting with the Framework
» Discovering Browser Capabilities ASP.NET and Web Forms: Developing Browser-Based Applications
» The Session Object Maintaining State
» The Application Object Maintaining State
» Session and Application Startup and Shutdown global.asax Compiles to a Class
» Adding Global Objects Application-Level Code and global.asax
» ASP.NET authorization Authorization
» Windows NTFS authorization Code-access authorization
» IUSR_ComputerName Impersonation Accessing Network Resources
» User Controls Designing Custom Controls
» Creating a custom server control using Visual Studio .NET
» Creating a custom server control in code Using a custom server control in Visual Studio .NET
» Summary ASP.NET and Web Forms: Developing Browser-Based Applications
» The WebService Attribute The WebMethod Attribute
» Testing a Web Service with a Browser
» Consuming a Web Service in Visual Studio .NET
» Consuming a Web Service in Notepad
» Synchronous Versus Asynchronous Calls
» Web-Service Descriptions Web-Service Discovery
» Limitations of Web Services Summary
» A Brief History of Universal Data Access Managed Providers
» Connecting to a SQL Server Database
» Connecting to an OLE DB Data Source
» The DataSet Class Finding Tables
» Finding Column Values Finding Column Definitions Changing, Adding, and Deleting Rows
» Writing Updates Back to the Data Source
» Relations Between DataTables in a DataSet
» The DataSets XML Capabilities
» Binding a DataSet to a Windows Forms DataGrid
» Binding a DataSet to a Web Forms DataGrid
» Typed DataSets ADO.NET: Developing Database Applications
» Reading Data Using a DataReader
Show more