Controls in VB2008 are useful objects that can be placed in the form to perform various tasks. They are used to create many kinds of Windows applications. The controls are available in a Toolbo, as shown in Figure 2.1 below:
The controls are categorized into Common Controls, Containers, Menus, Toolbars, Data, Components, Printings and Dialogs. At the moment, we will focus on the common controls. Some of the most used common controls are Button, Label, ComboBox, ListBox, PictureBox, TextBox etc. To insert a control into your form, you just need to drag the control and drop it into the form. You can reposition and resize it as you like. Let's examine a few programs that made use of Button, Label, TextBox , ListBox and PictureBox . You don't have to worry about the code yet, we will explain it later.
In this program, you insert two textboxes , three labels and one button. The two textboxes are for the users to enter two numbers, one label is to display the multiplication operator and the other label is to display the equal sign. The last label is to display the answer.
Dim num1, num2, product As Single num1 = TextBox1.Text num2 = TextBox2.Text product = num1 * num2 Label3.Text = product
This program will add one item at a time as the user enter an item into the TextBox and click the Add button.
Dim item As String item = TextBox1.Text ListBox1.Items.Add(item)
In this program, we insert a PictureBox and a Button into the form. Make sure to set the SizeMode property of the PictureBox to StretchImage so that the whole picture can be viewed in the picture box. Key in the code as shown below and you can load an image from a certain image file into the PictureBox.
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
'To load an image into the PictureBox from an image file
PictureBox1.Image = Image.FromFile("c:\Users\Public\Pictures\Sample Pictures\Frangipani Flowers.jpg")