Introduction

As you should know already, every class has a fundamental method called a default constructor. Every control of the .NET Framework is based on a class that has a default constructor and most of those classes have only one constructor: the default. The default constructor allows you to instantiate the class without necessarily initializing it. To use it, you must know the name of the control you want to use since each control bears the same name as its class. Here is an example:

Imports System
Imports System.Drawing
Imports System.Windows.Forms

Module Exercise

    Public Class WinControls
        Inherits Form

        Private btnReset As Button

        Dim components As System.ComponentModel.Container

        Public Sub New()
            InitializeComponent()
        End Sub

        Public Sub InitializeComponent()
            btnReset = New Button()
            
        End Sub

        Public Shared Function Main() As Integer

            Application.Run(New WinControls())
            Return 0

        End Function

    End Class

End Module

If you are not planning to use a control straight from the .NET Framework, you can also create your own class that is derived from the class of the control, as we have mentioned in previous lessons. 

As mentioned in the previous lesson, after instantiating a control, it is available but the user cannot see. Each control that acts as a parent of another control has a property called Controls. This property, which is a ControlCollection type, is equipped with an Add() method. If you want to display the new control to the user, you should pass it to the Control.Controls.Add() method. Here is an example:

Imports System
Imports System.Drawing
Imports System.Windows.Forms

Module Exercise

    Public Class WinControls
        Inherits Form

        Private btnReset As Button

        Dim components As System.ComponentModel.Container

        Public Sub New()
            InitializeComponent()
        End Sub

        Public Sub InitializeComponent()
            btnReset = New Button()

            Controls.Add(btnReset)
        End Sub

        Public Shared Function Main() As Integer

            Application.Run(New WinControls())
            Return 0

        End Function

    End Class

End Module

This displays the control to the user.

After using a control, it must be destroyed. Another detail of Windows controls is that they use or consume computer resources during their lifetime. When the controls are not used anymore, such as when their application closes, these resources should be freed and given back to the operating system to make them available to other controls. This task can be performed using the Dispose() method to the Control class, which can then be overridden by its child controls. The syntax of the Control.Dispose() method is:

Protected Overrides Sub Dispose(disposing As Boolean)

This method takes one argument, disposing, that indicates how the resources would be released. If this argument is passed with a False value, only the unmanaged resources would be released. If it is passed as True, then both managed and unmanaged resources would be released.

The Windows controls available from the .NET Framework and that we will user in our lessons. They are equipped with various methods ready to be used. Of course, no library can surely provide every single type of method that every programmer would use. For this reason, it will not be unusual that you need a method that is not available for a control you are using. In the same way, when you create a Windows Application that is based on a Form class, you will likely need a method that is not defined in the Form class. In this case, you can create your own and new method.

A method is created like a normal procedure. If you want to add it to a form, you can open the Code Editor and write your procedure outside of any existing procedure. Here is an example:

Imports System
Imports System.Drawing
Imports System.Windows.Forms

Module Exercise

    Public Class WinControls
        Inherits Form

        Private btnReset As Button

        Dim components As System.ComponentModel.Container

        Public Sub New()
            InitializeComponent()
        End Sub

        Public Sub InitializeComponent()
            btnReset = New Button()
            btnReset.Text = "Reset"
            btnReset.Location = New Point(20, 20)

            Controls.Add(btnReset)
        End Sub

        Private Function CalculateRectangleArea(ByVal Recto As Rectangle) As Double
            Return Recto.Width * Recto.Height
        End Function

        Public Shared Function Main() As Integer

            Application.Run(New WinControls())
            Return 0

        End Function

    End Class

End Module

In the same way, if you derive a class from one of the existing classes because you want to get a custom control from it, you can declare a new method as you see fit and use it appropriately.

Probably the best way is to let the Code Editor insert the new method based on your specifications. To do that, in the Class View, first expand the name of the project. Then, right-click the name of the class where you want to add a new method, position the mouse on Add, and click Add Method. This would open the C# Method Wizard dialog box you can fill out and click Finish. After the method's body has been defined you

Among all the languages of the .NET Framework and Microsoft Visual Studio, Visual Basic has the largest and the most impressive library of functions. There are so many of these functions, we cannot review them here.