Visual Basic.NET How to Program (PDF)

208 Procedures Chapter 6
playDie executes. We use the Image property (line 41) to display an image on a label. We
set the property’s value with an assignment statement (lines 41–43). Notice that we specify
the image to display through procedure FromFile in class Image (contained in the
System.Drawing namespace). Method Directory.GetCurrentDirectory
(contained in the System.IO namespace) returns the location of the folder in which the current
project is located, including bin, the directory containing the compiled project files. The
die images must be placed in this folder for the solutions in Fig. 6.15 and Fig. 6.16 to operate
properly. The graphics used in this example and several other examples in this chapter were
created with Adobe ® Photoshop Elements and are located in the project directory available
on the CD-ROM that accompanies this book and at www.deitel.com.
Notice that we must include an Imports directive (line 4) to use classes in
System.IO, but not to use classes in System.Drawing. By default, Windows applications
import several namespaces, including Microsoft.VisualBasic, System,
System.Drawing, System.Windows.Forms and System.Collections. The
se namespaces are imported for the entire project, eliminating the need for Imports directives
in individual project files. Other namespaces can be imported into a project via the
Property Pages dialog (opened by selecting Project > Properties from the menu bar)
in the Imports listing under Common Properties. Some of the namespaces imported
by default are not used in this example. For instance, we do not yet use namespace
System.Collections, which allows programmers to create collections of objects (see
Chapter 24, Data Structures and Collections).
The Windows application in Fig. 6.16 rolls 12 dice to show that the numbers generated
by class Random occur with approximately equal frequencies. The program displays the
cumulative frequencies of each face in a TextBox.
1 ' Fig. 6.14: RandomInteger.vb
2 ' Generating random integers.
3
4 Imports System.Windows.Forms
5
6 Module modRandomInteger
7
8 Sub Main()
9 Dim randomObject As Random = New Random()
10 Dim randomNumber As Integer
11 Dim output As String = ""
12 Dim i As Integer
13
14 For i = 1 To 20
15 randomNumber = randomObject.Next(1, 7)
16 output &= randomNumber & " "
17
18 If i Mod 5 = 0 Then ' is i a multiple of 5?
19 output &= vbCrLf
20 End If
21
22 Next
Fig. Fig. 6.14 6.14 Random integers created by calling method Next of class Random
(part 1 of 2).