3.1 The Control
writing an event procedure for the control to response to a user's input, you
have to set certain properties for the control to determine its appearance and
how it will work with the event procedure. You can set the properties of the
controls in the properties window at design time or at runtime.
Figure 3.1 on the right is
a typical properties window for a form. It refers particularly to
interface of the first program you have learned in the previous lesson, as shown in the Figure 3.2. The
title of the form is defined by the Text property and its default name is Form
1. To change the form's title to any name that you like, simple click in the box on
the right of the Text property and type in the new name, in this example, the
title is Multiplication. Notice that this title will appear on top of the
windows. In the properties window, the item
appears at the top part is the object currently selected (in Figure 3.1,
the object selected is Form1). At the bottom part, the items listed in
the left column represent the names of various properties associated
with the selected object while the items listed in the right column
represent the states of the properties.
Properties can be set by highlighting the items in the right column then change them by typing or selecting the options available.
You can also change the
properties of the object at runtime to give special effects such as change of color,
shape, animation effect and so on. For example the following code will
change the form color to yellow every time the form is loaded. VB2008 uses RGB(Red, Green, Blue) to determine the colors. The RGB code for yellow is
255,255,0. Me in the code refer to the current form and Backcolor is the
property of the form's background color. The formula to assign the RGB color
to the form is Color.FormArbg(RGB codes).
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
Me.BackColor = Color.FromArgb(255, 255, 0)0)
also use the follow procedure to assign the color at run time.
Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs)
Me.BackColor = Color.Yellow
Both procedures above will load the form with a yellow background as shown in Figure 3.3:
are some of the common colors and the corresponding RGB codes. You can
always experiment with other combinations, but remember the maximum number for
each color is 255 and the minimum number is 0.
255, 255, 0
255, 165, 0
0, 255, 255
0, 0, 0
0, 0, 255
255, 0, 255
255, 255, 255
The following is another program
that allows the user to enter the RGB codes into three different textboxes and
when he/she clicks the display color button, the background color of the
form will change according to the RGB codes. So, this program allows users to
change the color properties of the form at run time.
Private Sub Button1_Click(ByVal
sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim rgb1, rgb2, rgb3 As
rgb1 = TextBox1.Text
rgb2 = TextBox2.Text
rgb3 = TextBox3.Text
Me.BackColor = Color.FromArgb(rgb1, rgb2, rgb3)