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Introduction to Visual Basic Winforms

In this part of the Visual Basic Winforms programming tutorial, we will introduce the Winforms library and create our first programs using the Visual Basic programming language.

The purpose of this tutorial is to get you started with the Winforms and Visual Basic. Images used in this tutorial can be downloaded here. I used some icons from the tango icons pack of the Gnome project.

About

Windows Forms is a graphical user interface application programming interface (API) included as a part of Microsoft's .NET Framework. As of 13 May 2008, Mono's System.Windows.Forms 2.0 is API complete. Simply put, Winforms is a library for creating GUI applications.

Mono is a cross platform, open source .NET development framework. It is a .NET compatible set of tools, which include C# compiler, Visual Basic compiler, Common Language Runtime, ADO.NET, ASP.NET and Winforms libraries.

vbnc -r:/usr/lib/mono/2.0/System.Windows.Forms.dll quitbutton.vb

The above command shows, how to compile the quitbutton example. The -r parameter of the mono VB compiler loads the Winforms assembly. It is a dynamic library. The commnad shows a path to the dll library on a Ubuntu system.

Centering a window

In the second example, we will center the window on the screen.


' ZetCode Mono Visual Basic Winforms tutorial
'
' This program centers a window
' on the screen
'
' author jan bodnar
' last modified May 2009
' website www.zetcode.com


Imports System.Windows.Forms
Imports System.Drawing


Public Class WinVBApp
    Inherits Form

    Public Sub New

       Me.Text = "Center"
       Me.Size = New Size(250, 200)
       Me.CenterToScreen

    End Sub


   Public Shared Sub Main
        Application.Run(New WinVBApp)
   End Sub
   
End Class

This code example shows a small window in the center of the screen.

 Imports System.Windows.Forms
 Imports System.Drawing

The Imports keyword imports necessery types that we will use in the application.

 Public Class WinVBApp
     Inherits Form

In Winforms, any window or a dialog is a Form. This control is a basic container, whose purpose is to display other child controls. Our class inherits from a form. This way it becomes a form itself.

 Public Sub New
 ...
 End Sub

In the constructor, we set up the application.

 Me.Text = "Center"

Here we set a title for the form.

 Me.Size = New Size(250, 200)

We set a size for the form.

 Me.CenterToScreen

This code line centers a window on the screen.

 Public Shared Sub Main
     Application.Run(New WinVBApp)
 End Sub

We run the example.

Icon

Mono means monkey in Spanish. If we do not provide an icon for our application, we have a head of a monkey by default. The next example shows, how to change this.


' ZetCode Mono Visual Basic Winforms tutorial
'
' This program shows an icon in the
' title bar
'
' author jan bodnar
' last modified May 2009
' website www.zetcode.com


Imports System.Windows.Forms
Imports System.Drawing

Public Class WinVBApp
    Inherits Form

    Public Sub New
    
       Me.Text = "Icon"
       Me.Size = New Size(250, 200)

       Try 
           Icon = New Icon("web.ico")
       Catch e As Exception
           Console.WriteLine(e.Message)
           Environment.Exit(1)
       End Try
       
       Me.CenterToScreen
       
    End Sub

    Public Shared Sub Main
        Application.Run(New WinVBApp)
    End Sub
   
End Class

The code example shows an icon in the upper left corner of the form. A form's icon is the picture that represents the form in the taskbar as well as the icon that is displayed for the control box of the form.

 Try 
     Icon = New Icon("web.ico")
 Catch e As Exception
     Console.WriteLine(e.Message)
     Environment.Exit(1)
 End Try

It is a good practice to put all input output work between the Try/Catch keywords. The web.ico file must be available in the current working directory. This is the directory from where we execute (./icon.exe) our application.

Figure: Icon

Quit button

In the last example of this section, we will create a quit button. When we press this button, the application terminates.


' ZetCode Mono Visual Basic Winforms tutorial
'
' This program creates a quit
' button. When we press the button,
' the application terminates. 
'
' author jan bodnar
' last modified May 2009
' website www.zetcode.com


Imports System.Windows.Forms
Imports System.Drawing


Public Class WinVBApp
    Inherits Form

    Public Sub New

       Me.Text = "Quit button"
       Me.Size = New Size(250, 200)
       
       Me.InitUI
       
       Me.CenterToScreen

    End Sub
    
    Private Sub InitUI
    
        Dim button As New Button

        button.Location = New Point(30, 20)
        button.Text = "Quit"
        button.Parent = Me

        AddHandler button.Click, AddressOf Me.OnClick
        
        Me.CenterToScreen
        
    End Sub

    Private Sub OnClick(ByVal sender As Object, ByVal e As EventArgs)
       Me.Close
    End Sub


    Public Shared Sub Main
        Application.Run(New WinVBApp)
    End Sub
   
End Class

We use the Button. This is a very common widget. It is a rectangular and usually shows a text label.

 Me.InitUI

We delegate the creation of the user interface to the InitUI method.

 Dim button As New Button

 button.Location = New Point(30, 20)
 button.Text = "Quit"
 button.Parent = Me

We create the button widget. We position it on the form. Provide a label for it and put it inside the form container.

 AddHandler button.Click, AddressOf Me.OnClick

When we click on the button, the Click event is triggered. We react to this event with the OnClick method.

 Private Sub OnClick(ByVal sender As Object, ByVal e As EventArgs)
     Me.Close
 End Sub

The OnClick method terminates the application.

Figure: Quit button

This section was an introduction to the Winforms library with the Visual Basic language.

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