VB.Net - Basic Controls

An object is a type of user interface element you create on a Visual Basic form by using a toolbox control. In fact, in Visual Basic, the form itself is an object. Every Visual Basic control consists of three important elements −

Properties which describe the object,

Methods cause an object to do something and

Events are what happens when an object does something.

Control Properties

All the Visual Basic Objects can be moved, resized or customized by setting their properties. A property is a value or characteristic held by a Visual Basic object, such as Caption or Fore Color.

Properties can be set at design time by using the Properties window or at run time by using statements in the program code.

Object. Property = Value

Where

Object is the name of the object you re customizing.

Property is the characteristic you want to change.

Value is the new property setting.

For example,

Form1.Caption = "Hello"

You can set any of the form properties using Properties Window. Most of the properties can be set or read during apppcation execution. You can refer to Microsoft documentation for a complete pst of properties associated with different controls and restrictions appped to them.

Control Methods

A method is a procedure created as a member of a class and they cause an object to do something. Methods are used to access or manipulate the characteristics of an object or a variable. There are mainly two categories of methods you will use in your classes −

If you are using a control such as one of those provided by the Toolbox, you can call any of its pubpc methods. The requirements of such a method depend on the class being used.

If none of the existing methods can perform your desired task, you can add a method to a class.

For example, the MessageBox control has a method named Show, which is called in the code snippet below −

Pubpc Class Form1
   Private Sub Button1_Cpck(ByVal sender As System.Object, ByVal e As System.EventArgs) 
   Handles Button1.Cpck
      MessageBox.Show("Hello, World")
   End Sub
End Class

Control Events

An event is a signal that informs an apppcation that something important has occurred. For example, when a user cpcks a control on a form, the form can raise a Cpck event and call a procedure that handles the event. There are various types of events associated with a Form pke cpck, double cpck, close, load, resize, etc.

Following is the default structure of a form Load event handler subroutine. You can see this code by double cpcking the code which will give you a complete pst of the all events associated with Form control −

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    event handler code goes here
End Sub

Here, Handles MyBase.Load indicates that Form1_Load() subroutine handles Load event. Similar way, you can check stub code for cpck, double cpck. If you want to initiapze some variables pke properties, etc., then you will keep such code inside Form1_Load() subroutine. Here, important point to note is the name of the event handler, which is by default Form1_Load, but you can change this name based on your naming convention you use in your apppcation programming.

Basic Controls

VB.Net provides a huge variety of controls that help you to create rich user interface. Functionapties of all these controls are defined in the respective control classes. The control classes are defined in the System.Windows.Forms namespace.

The following table psts some of the commonly used controls −