To Notes

Summary for IT 236 on 6/13/06

Go over IT 236 course web site

• See table of contents to left:
  Announcements, Lecture Summaries, Prof Info, Course Syllabus, Course Materials, VB.NET Examples, Takehome Quizzes, Projects, Exam Info, Grades Online.

About VB.NET.

• Visual Basic was first introduced in 1991 with VB Version 1, followed by versions 2 through 6 in 1992 to 1998.

• Versions 4, 5, and 6 were backward compatable; code in one version could be run in a later version.

• The VB.NET Beta1 Version was introduced in 2001.

• VB.NET is not backward compatable. VB6 projects must be upgraded to allow them to run in VB.NET.

• VB.NET is as much like Java than VB6.
  
  Form and control creation code is available to programmer
  Parameterized constructors and inheritance are available
  The just-in-time (JIT) interpreter is similar to Java's virtual machine.

• In this class, the examples will be given in the 2003 Version of .Net.

• You may use either Version 2003 or 2005 to complete the Projects.

• A Java -- Visual Basic Dictionary

Creating a ClickCounter Application

1. Invoke the .NET IDE (Interactive Development Environment). By double clicking on the .Microsoft Visual Studio .NET 2003 Icon. In the computer labs, Select Start >> All Programs >> Microsoft Visual Studio .NET 2003 >> Microsoft Visual Studio .NET 2003

2. Close the Start Page if it appears by clicking on the X to the right of the Start Page Tab.

3. Select File >> New >> Project. Browse to the correct folder (lower right), say IT236. Make sure that Visual Basic Projects (upper left) and Windows Application (upper right) are selected. Enter the name of the project, ClickCounter. Click OK.

4. From the ToolBox, drag a TextBox control onto the form. The name of the textbox will be TextBox.

5. In the Properties Window for the textbox, change the name to txtNumberOfClicks. Also change its Text property from TextBox1 to "0".

6. From the ToolBox, drag a Button control onto the form. The name of the button will be Button1.

7. In the Properties Window for the button, change the name to btnButton. Also change its Text property from Button1 to "Push Me".

8. Double click the button to produce the header and terminator for the Click event handler:

   Private Sub btnButton_Click(ByVal sender As System.Object, _
       ByVal e As System.EventArgs) Handles btnButton.Click

   End Sub

9. Add the body of the event handler so the code looks like this:

   Private Sub btnButton_Click(ByVal sender As System.Object, _
       ByVal e As System.EventArgs) Handles btnButton.Click

       txtNumberOfClicks.Text = txtNumberOfClicks.Text + 1
   End Sub

10. Run the application by selecting Debug and Start.

Important Features of the Visual Studio .NET

• Main menu (File, Edit, View, Project, Build, Debug, Tools, Window, Help)

• Windows are dockable

• AutoHide is available for some windows.

• Solution Explorer

• Form and Code Windows

• Properties Window

• Toolbox

• Online Help (Contents, Index, Dynamic)

Running the VB.NET Examples

• To Run the VB.NET Console Example HelloWorld1:
  1. Select File, New, Project.

  2. Browse to the correct folder (lower right). Make sure that Visual Basic Projects (upper left) and Console Application (upper right) are selected. Enter the name of the project, say HelloWorld1. Click OK.

  3. Using the Internet Explorer, select Examples in the links on the left of the IT 236 course page.

  4. Find the example HelloWorld1. Select the link for Form1.

  5. Use Ctrl-A to select all of the source code, and Ctrl-C to copy it.

  6. Go back to the VB.NET IDE, click on the Code Window, select all of the code with Ctrl-A, and use Ctrl-V to replace the old code with the new code copied from the HelloWorld1 source code.

  7. Select Debug >> Start to run the project. You should see "Hello World." in a new Command Window.

• List some things you notice about the VB.NET language from the HelloWorld1 example.
  1. No semicolon at the end of the line.

  2. Use System.Console.WriteLine to print to the screen.

  3. Use _ as the line continuation character.

  4. Use an apostrophe ( ' ) to start a comment line.

  5. Ampersand (&) means string concatenation.

  6. No curly braces are used as in Java and C++. End statements are used instead to terminate a block.

  7. Using Option Strict On insures that automatic type conversions are not performed.

A HelloWorld Console Application

• Look at the HelloWorld1 example.

• A Console Application displays output in a command window (also known as a DOS window).

• A HelloWorld program is traditionally the first program that a person writes in a new computer language.

• Here is the HelloWorld1 example program in VB.NET, with no comments:

  Public Module Module1
      Public Sub Main()
         System.Console.WriteLine("Hello, World.")
         System.Console.ReadLine()
      End Sub
  End Module

• A console application is usually prescriptive. The code tells the application, in step-by-step form, what to do and the application does it.

A HelloWorld Windows Application

• Identify these controls on the Internet Explorer Browser print dialog.
  Button, TextBox, CheckBox, RadioButton, UpDown, GroupBox, Label, ListView.

• HelloWorld2 is a Windows Application. The output message is displayed in a label control.

• Select the Label control from the Toolbox. Then draw the control on the form by pressing the mouse at the upper left corner of the bounding rectangle for the control and releasing the mouse at the lower right corner of the bounding rectangle.

• Use the Properties Window to change control properties.

• When a new control is created, the first two properties to change are Name and Text.

• A Windows application is usually reactive. It waits for the user to take an action (like clicking on a button), then reacts to the action.

• The procedure that executes in response to an event is called an event handler.

• Procedures are called methods when using object oriented terminology.

Submitting Projects

• Install VB.Net Professional Edition from disk included with textbook.

• Use CTI Course Online Web site to submit projects and takehome quizzes.

• Look at the Projects Page.

• Look at the Project Submission Guidelines every time you submit a project.
  For example, there is a penalty for not including comments in your project or for not indenting your code properly.

The Greeter Project

• Look at the Greeter1 and Greeter2 examples.

• Look at the DisplayImage example.

• Discuss the Greeter Project.

Review of Objects

• An object contains data (called properties) and procedures (called methods) for manpulating that data.

• A property is a piece of data contained in an object.

• A method is a procedure that the object can execute to accomplish a task.

• An event is something that happens to an object. The object can respond to an event by executing a method called an event handler.

• A class is a template for creating objects.

• Generally, properties distinguish an object from all other objects of the same class. They are not usually features which are identical for all objects of that class.

• Other object oriented languages have different terms for properties. C++ uses the term data member and Java uses the term instance variable.

• Object oriented programming was invented by Alan Kay, then at Xerox, in 1971. He invented object oriented programming in the context of the language SmallTalk.

• Here are some examples of objects in everyday life.