Another common type of application in visual basic.net application is the console application and we'll be using such application during next feww hours as we study the visual basic languauge . to create a console application you select
File>> New project>>Console Application
There,s no user interface in console application: the output of such an application simply appears directly in a DOS window as text
The Sub Main() and End Sub part here is visual Basic's way of creating a sub procedure (the detail of sub procedure we explain later) .That name is Main here ,and code with that name is automatically run when a console Application starts. We can put the code we want to execute when the console application runs in the Main Sub procedure. For example,to display the message "Hello There "--- we can use this line of code
module Module1
Sub Main()
Console.writeline("Hello There")
end Sub()
Because console application dont have textboxs or user - interface element you cant display text in such application.instead, you can use Console.writeline to write linews of text.
you can now run this new console application in usual way--select Debug,Start menu item or by pressing F5 . A DOS Window will appear with the text "Hello There" in it.But it'll close as fast as it opened,You can solve this problem by intentionally keeping the console widow open until you're ready to dismiss it ----for example until to press Enter Key. and you do that by inserting the Console.readline() code.Such lines of text are read when you press the Enter Key ,ending your input. to make this work .we can display a prompt saying "Press Enter To Continue..."
and then use Console.Readline() to wait until the Enter key is pressed.It Look like this
Module Module1
Sub Main()
Console.WriteLine("hello there")
Console.WriteLine("Press Enter To Continue...")
Console.ReadLine()
End Sub
End Module
and thats all we need! You can see the increament of new line code in below picture 26
When you run application by pressing F5 or using Debug ,Start you will see the result like the below figure27
Console Application like thes provide you an easy way of working with Visual Basic without worrying about the detail of creating and handling a user interface.All you to do is to display text to use Console.Writeline(), and to read what user has typed, you use Console.Readline
Wednesday, January 21, 2009
VB.net2008:Creating Console Application
Tuesday, January 20, 2009
Visual Studio2008: Comments
Comments are parts of a program that are ignored by the Visual Basic 2008 compiler, which means you can write whatever you like in them, be it English, C#, Perl, FORTRAN, Chinese, whatever. What they ’ re supposed to do is help the human developer reading the code understand what each part of the code is supposed to be doing.
All languages support comments, not just Visual Basic 2008. If you ’ re looking at C# code, for example,you ’ ll find that comments start with a double forward slash ( // ).
In Visual Basic 2008, you begin your comments with an apostrophe ('). Anything on the same line following that apostrophe is your comment. You can also add comments onto a line that already has code, like this:
intNumber = intNumber + 1 'Add 1 to the value of intNumber
This works just as well, because only comments (not code) follow the apostrophe. Note that the
comments in the preceding code, more or less, match the algorithm. A good technique for
adding comments is to write a few words explaining the stage of the algorithm that ’ s being expressed as software code.
Comments are primarily used to make the code easier to understand, either to a new developer who ’ s never seen your code before or to you when you haven ’ t reviewed your code for a while. The purpose of a comment is to point out something that might not be immediately obvious or to summarize code to enable the developer to understand what ’ s going on without having to ponder each and every line.
You ’ ll find that programmers have their own guidelines about how to write comments. If you work for a larger software company, or your manager/mentor is hot on coding standards, they will dictate which formats your comments should take and where you should and should not add comments to the code.
"The compiler ignores whitespace and comments, so there are no performance differences between codewith lots of whitespace and comments, and code with none."
Visual Studio2008: Explaination of Variable Woking
The program starts at the top and works its way down, one line at a time, to the bottom. The first line defines a new variable, called intNumber :
Dim intNumber As Integer
Dim is a keyword.A keyword has a special meaning in Visual Basic 2008 and is
used for things such as commands. Dim tells Visual Basic 2008 that what follows is a variable
definition.
As Integer tells Visual Basic 2008 what kind of value you want to store in the variable. This is
known as the data type . For now, all you need to know is that this is used to tell Visual Basic 2008 that you expect to store an integer (whole number) value in the variable.
The next line sets the value of intNumber :
The next statement simply adds 1 to the variable intNumber :
intNumber = intNumber + 1
What this line actually means is: Keep the current value of intNumber and add 1 to it.
The final line displays a message box with the text Value of intNumber + 1 = and the current
value of intNumber . You ’ ve also set the title of the message box to Variables to match the project name. When using numeric variables in text, it is a good idea to use the ToString method to cast the numeric value to a string. This prevents the compiler from having to figure out that this is a number and then converting that number to a string so it can be displayed:
MessageBox.Show("Value of intNumber + 1 = " & intNumber.ToString, _
"Variables")
Visual Studio2008:Variables And Its Working
A variable is something that you store a value in as you work through your project. You can then
make a decision based on that value (for example, “ Is it equal to 7? ” or “ Is it more than 4? ” ), or you can perform operations on that value to change it into something else (for example, “ Add 2 to the value ” , “ Multiply it by 6 ” , and so on).
1. Create a new project in Visual Studio 2008 by selecting File New Project from the menu bar.
In the New Project dialog box, select Windows Forms Application from the right - hand pane
and enter the project name as Variables and click OK (see Figure 21).
2. Make Form1 a little smaller and add a Button control from the Toolbox to it. Set the button ’ s
Text property to Add 1 to intNumber and its Name property to btnAdd. Your form should
look similar Figure 22 .
3. Double - click the button to open the btnAdd_Click event handler. Add the following
highlighted code to it:
Private Sub btnAdd_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles btnAdd.Click
Dim intNumber As Integer intNumber = 27 intNumber = intNumber + 1 MessageBox.Show("Value of intNumber + 1 = " & intNumber.ToString, _ “Variables”)
End Sub
4. Click the Save All button on the toolbar, verify the information in the Save Project dialog box,
and then click the Save button to save your project.
5. Run the project, click the Add 1 to intNumber button, and you ’ ll see a message box like the
one in Figure 23 .
Monday, January 19, 2009
Visual Studio 2008: Using the Help System
The Help system included in Visual Basic 2008 is an improvement over the Help systems in earlier versions.As you begin to learn Visual Basic 2008, you will probably become very familiar with the Help system.However, it is worthwhile to give you an overview, just to help speed your searches for information.
The Help menu contains the items shown in Figure 20 .
As you can see, this menu contains a few more items than the typical Windows application. The main reason for this is the vastness of the documentation. Few people could keep it all in their heads — but luckily, that is not a problem, because you can always quickly and easily refer to the Help system. Think of it as a safety net for your brain.
One really fantastic feature is Dynamic Help. When you select the Dynamic Help menu item from the Help menu, the Dynamic Help window is displayed as a tab behind the Properties window, with a list of relevant topics for whatever you may be working on.
Suppose you are working with a text box (perhaps the text box in the HelloUser application) and want to find out some information; you just select the text box on your form or in the code window and then use Dynamic Help to see all the help topics that pertain to text boxes, as shown in Figure 21 .
The other help commands in the Help menu (Search, Contents, and Index), function just as they wouldin any other Windows application. The How Do I menu item displays the Visual Studio Help collectionwith a list of common tasks that are categorized. This makes finding help on common tasks fast andefficient.
Visual Studio 2008: Working Of Code In "Hello User" Project
The code that you added to the Click event for the OK button will take the name that was entered inthe text box and use it as part of the message that was displayed in Figure 20.
The first line of text you entered in this procedure (‘Display a message box greeting to the
user) is actually a comment, text that is meant to be read by the human programmer who is writing or maintaining the code, not by the computer. Comments in Visual Basic 2008 begin with a single quote ('), and everything following on that line is considered a comment and ignored by the compiler.
The MessageBox.Show method displays a message box that accepts various parameters. As used in your code, you have passed the string text to be displayed in the message box. This is accomplished through the concatenation of string constants defined by text enclosed in quotes. Concatenation of strings into one long string is performed through the use of the ampersand (&) character.
The code that follows concatenates a string constant of "Hello," followed by the value contained in the Text property of the txtName text box control followed by a string constant of “! Welcome to Visual Basic 2008.”. The second parameter being passed to the MessageBox.Show method is the caption to be used in the title bar of the Message Box dialog box.
Finally, the underscore (_) character used at the end of the lines in the following code enables you to split your code onto separate lines. This tells the compiler that the rest of the code for the parameter is continued on the next line. This is really useful when building long strings, because it allows you to view the entire code fragment in the Code Editor without having to scroll the Code Editor window to the right to view the entire line of code.
Private Sub btnOK_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles btnOK.Click
'Display a message box greeting to the user
MessageBox.Show(“Hello,” & txtName.Text & _
“! Welcome to Visual Basic 2008.”, _
“Hello User Message”)
End Sub
The next procedure that you added code for was the Exit button’s Click event. Here you simply enter the code: Me.Close(). As explained earlier, the Me keyword refers to the form itself. The Close method of the form closes the form and releases all resources associated with it, thus ending the program.
Private Sub btnExit_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles btnExit.Click
‘End the program and close the form
Me.Close()
End Sub
Visual Studio2008: Put Coding in "Hello User" Project
1. To begin adding the necessary code, click the Design tab to show the form again. Then
double-click the OK button. The code window will open with the following code. This is the
shell of the button’s Click event and is the place where you enter the code that you want to
run when you click the button. This code is known as an event handler and sometimes is also
referred to as an event procedure:
Private Sub btnOK_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
End Sub
As a result of the typographic constraints in publishing, it is not possible to put the Sub
declaration on one line. Visual Basic 2008 allows you to break up lines of code by using the
underscore character (_) to signify a line continuation. The space before the underscore is
required. Any whitespace preceding the code on the following line is ignored.
Sub is an example of a keyword. In programming terms, a keyword is a special word that is
used to tell Visual Basic 2008 to do something special. In this case, it tells Visual Basic 2008
that this is a subroutine, a procedure that does not return a value. Anything that you type between the lines Private Sub and End Sub will make up the event procedure for the OK
button.
2. Now add the code into the procedure:
'Display a message box greeting to the user MessageBox.Show("Hello, " & txtName.Text & _ “! Welcome to Visual Basic 2008.”, _ “Hello User Message”)
End Sub
3. After you have added the preceding code, go back to the Design tab, and double-click the Exit
button. Add the following code to the btnExit_Click event procedure:
Private Sub btnExit_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles btnExit.Click
'End the program and close the form
Me.Close()
End Sub
You may be wondering what Me is. Me is a keyword that refers to the form. Just like the pronoun me, it is just shorthand for referring to one’s self.
4. Now that the code is finished, the moment of truth has arrived and you can see your creation.
First, however, save your work by using File >> Save All from the menu or by clicking the Save
All button on the toolbar. The Save Project dialog box is displayed as shown in Figure 18,
prompting you for a name and location for saving the project.
By default, a project is saved in a folder with the project name; in this case Hello User. Since
this is the only project in the solution, there is no need to create a separate folder for the
solution which contains the same name as the project, thus the Create directory for solution
check box has been unchecked.
5. Now click the Start button on the toolbar. You will notice a lot of activity in the Output
window at the bottom of your screen. Provided that you have not made any mistakes in entering
the code, this information just lets you know which files are being loaded to run your
application.
At this point Visual Studio 2008 will compile the code. Compiling is the activity of taking
the Visual Basic 2008 source code that you have written and translating it into a form that the
computer understands. After the compilation is complete, Visual Studio 2008 runs (also
known as executes) the program, and you’ll be able to see the results.
Any errors that Visual Basic 2008 encounters will be displayed as tasks in the Task List window.
Double-clicking a task transports you to the offending line of code. You will learn more about how
to debug the errors in your code in the site.
6. When the application loads, you see the main form. Enter a name and click OK or press the
Alt+O key combination (see Figure 19).
A window known as a message box appears as shown in Figure 20, welcoming the person
whose name was entered in the text box on the form — in this case Stephanie.
Visual Studio2008: Coding Environment
The Code Editor:
Now that you have the HelloUser form defined, you have to add some code to make it actually do something interesting. You have already seen how easy it is to add controls to a form. Providing the functionality behind those on - screen elements is no more difficult. To add the code for a control, you just double - click the control in question. This opens the code editor in the main window, shown in Figure 17.
Note that an additional tab has been created in the main window. Now you have the Design tab and the Code tab, each containing the name of the form you are working on. You draw the controls on your form in the Design tab, and you write code for your form in the Code tab. One thing to note here is that Visual Studio 2008 has created a separate file for the code. The visual definition and the code behind it exist in separate files: HelloUser.Designer.vb and HelloUser.vb . This is actually the reason why building applications with Visual Basic 2008 is so slick and easy. Using the Design view you can visually lay out your application, and then, using Code view, you add just the bits of code to implement your desired functionality.
Note also that there are two combo boxes at the top of the window. These provide shortcuts to the various parts of your code. Hover your mouse on the combo box on the left, and you ’ ll see a tooltip appear, telling you that it is the Class Name combo box. If you expand this combo box, you will see a list of all the objects within your application. If you hover your mouse on the combo box on the right, you ’ ll see a tooltip telling you that this is the Method Name combo box. If you expand this combo box, you will see a list of all defined functions and subroutines for the object selected in the Class Name combo box. If this particular form had a lot of code behind it, these combo boxes would make navigating to the desired code area very quick — jumping to the selected area in your code. However, since all of the code for this project so far fits in the window, there are not a lot of places to get lost.
Visual Studio2008:Adding Control to "Hello User" Application(Cont.)
1. Stop the project if it is still running, because you now want to add some controls to your form.
The simplest way to stop your project is to click the close (X) button in the top-right corner of
the form. Alternatively, you can click the blue square on the toolbar (which displays a ToolTip
that says “Stop Debugging” if you hover over it with your mouse pointer).
2. Add a Label control to the form. Click Label in the Toolbox, drag it over to the form’s
Designer and drop it in the desired location. (You can also place controls on your form by
double-clicking the required control in the Toolbox or clicking the control in the Toolbox and
then drawing it on the form.)
3. If the Label control you have just drawn is not in the desired location, it really isn’t a problem.
When the control is on the form, you can resize it or move it around. Figure 12 shows what
the control looks like after you place it on the form. To move it, click the dotted border and
drag it to the desired location. The label will automatically resize itself to fit the text that you
enter in the Text property.
4. After drawing a control on the form, you should at least configure its name and the text that
it will display. You will see that the Properties window to the right of the Designer has
changed to Label1, telling you that you are currently examining the properties for the label.
In the Properties window, set your new label’s Text property to Enter Your Name. Note that,
once you press Enter or click on another property, the label on the form has automatically
resized itself to fit the text in the Text property. Now set the Name property to lblName.
5. Now, directly beneath the label, you want to add a text box, so that you can enter a name. You
are going to repeat the procedure you followed for adding the label, but this time make sure
you select the TextBox control from the toolbar. After you have dragged and dropped
(or double-clicked) the control into the appropriate position as shown in Figure 13, use
the Properties window to set its Name property to txtName.
Notice the sizing handles on the left and right side of the control. You can use these handles to
resize the text box horizontally.
6. In the bottom left corner of the form, add a Button control in exactly the same manner as you
added the label and text box. Set its Name property to btnOK and its Text property to &OK.
Your form should now look similar to the one shown in Figure 1-14.
The ampersand (&) is used in the Text property of buttons to create a keyboard shortcut (known as a hot key). The letter with the & sign placed in front of it will become underlined (as shown in Figure 14) to signal users that they can select that button by pressing the Alt+letter key combination, instead of using the mouse (on some configurations the underline doesn’t appear until the user presses Alt). In this particular instance, pressing Alt+O would be the same as clicking the OK button. There is no need to write code to accomplish this.
7. Now add a second Button control to the bottom right corner of the form by dragging the Button control from the Toolbox onto your form. Notice that, as you get close to the bottom right
of the form, a blue snap line appears, as shown in Figure 15. This snap line allows you to
align this new Button control with the existing Button control on the form. The snap lines
assist you in aligning controls to the left, right, top, or bottom of each other, depending on
where you are trying to position the new control. The light blue line provides you with a consistent margin between the edge of your control and the edge of the form. Set the Name property to btnExit and the Text property to E&xit. Your form should look similar to Figure 16.
Toolbox In Visual Studio 2008
❑ Toolbox: The Toolbox contains reusable controls and components that can be added to your application. These range from buttons to data connectors to customized controls that you have either purchased or developed.
The Toolbox is accessed through the View > Toolbox menu option, by clicking the Toolbox icon on the Standard menu bar, or by pressing Ctrl+Alt+X. Alternatively, the Toolbox tab is displayed on the left of the IDE; hovering your mouse over this tab will cause the Toolbox window to fly out, partially covering your form.
The Toolbox contains a Node type view of the various controls and components that can be placed onto your form. Controls such as text boxes, buttons, radio buttons, and combo boxes can be selected and then drawn onto your form. For the HelloUser application, you will be using only the controls in the Common Controls node. Figure 11 shows a listing of common controls for Windows Forms.
Controls can be added to your forms in any order, so it does not matter if you add the label control after the text box or the buttons before the label.
Visual Studio 2008: Creating Your First Application("Hello User")
Now you are going to create a very simple application called HelloUser that will allow you to enter a person ’ s name and display a greeting to that person in a message box.
1. Click the New Project button on the toolbar.
2. In the the New Project dialog box, select Visual Basic in the Project Types tree-view box to the left and then select Windows beneath it. The Templates box on the right will display all of the available templates for the project type chosen. Select the Windows Forms Application template.
Finally, type Hello User in the Name text box and click OK. Your New Project dialog box should look like Figure 7.
Visual Studio 2008 allows you to target your application to a specific version of the Microsoft .NET Framework. The combo box in the upper right corner of the New Project dialog box has version 3.5 selected, but you can target your application to version 3.0 or even version 2.0 of the .NET Framework.
The IDE will then create an empty Windows application for you. So far, your Hello User
program consists of one blank window, called a Windows Form (or sometimes just a form),
with the default name of Form1.vb, as shown in Figure 8.
Whenever Visual Studio 2008 creates a new file, either as part of the project creation process or
when you create a new file, it will use a name that describes what it is (in this case, a form)
followed by a number.
At this point, you can see that the various windows in the IDE are beginning to show their purposes, and you should take a brief look at them now before you come back to the Try It Out exercise. Note that if any of these windows are not visible on your screen, you can use the View menu to show them. Also, if you do not like the location of any particular window, you can move it by clicking its title bar (the blue bar at the top) and dragging it to a new location. The windows in the IDE can float (stand out on their own) or be docked (as they appear in Figure 8 ). The following list introduces the most common windows:
Next you’ll give your form a name and set a few properties for it.
1. Change the name of your form to something more indicative of what your application is.
Click Form1.vb in the Solution Explorer window. Then, in the Properties window, change the
File Name property from Form1.vb to HelloUser.vb and press Enter, as shown in Figure 1-9.
When changing properties you must either press Enter or click on another property for it to
take effect.
2. Note that the form’s file name has also been updated in the Solution Explorer to read
HelloUser.vb.
3. Click the form displayed in the Design window. The Properties window will change to
display the form’s Form properties (instead of the File properties, which you have just been
looking at). You will notice that the Properties window is dramatically different. The difference
is the result of two different views of the same file. When the form name is highlighted in
the Solution Explorer window, the physical file properties of the form are displayed. When the
form in the Design window is highlighted, the visual properties and logical properties of
the form are displayed.
The Properties window allows you to set a control’s properties easily. Properties are a
particular object’s set of internal data; they usually describe appearance or behavior. In
Figure 1-10 you can see that properties are displayed alphabetically. The properties can also
be grouped together in categories — Accessibility, Appearance, Behavior, Data, Design,
Focus, Layout, Misc, and Window Style.
4. Right now, the title (Text property) of your form (displayed in the bar at the top) is Form1.
This is not very descriptive, so change it to reflect the purpose of this application. Locate the
Text property in the Properties window. Change the Text property’s value to Hello from
Visual Basic 2008 and press Enter. Note that the form’s title has been updated to reflect the
change.
If you have trouble finding properties, click the little AZ icon on the toolbar toward the top of the
Properties window. This changes the property listing from being ordered by category to being
ordered by name.
5. You are now finished with the procedure. Click the Start button on the Visual Studio 2008
toolbar (the green triangle) to run the application. As you work through the book, whenever
we say “run the project” or “start the project,” just click the Start button. An empty window
with the title Hello from Visual Basic 2008 is displayed.
Monday, January 12, 2009
Installing Visual Basic 2008
1. The Visual Studio 2008 DVD has an auto-run feature, but if the Setup screen does not appear
after inserting the DVD, you need to run Setup.exe from the root directory of the DVD. To do
this, click the Windows Start menu at the bottom left of your screen and then select the Run
start menu item or browse to the Setup program on the DVD. In the Run dialog box, you can
click the Browse button to locate the setup.exe program on your DVD. Then click the OK
button in the Run dialog box to start the setup program. After the setup program initializes,
2. The dialog box shown in above picture shows the order in which the installation will occur. To
function properly, Visual Studio 2008 requires various updates to be installed depending on
the operating system that you have (for example, Service Pack 2 on Windows XP). The setup
program will automatically inform you of these updates if they are not installed. You should
install those updates first and then return to the Visual Studio 2008 setup program. The
individual updates required are different from the service releases listed as the third option in
above picture. Step 1 of the setup program will install Visual Studio 2008 so click the Install Visual Studio 2008 link shown in Figure .
3. The next step in the installation process asks you if you want to send the setup information from the installation of Visual Studio 2008 to Microsoft. This is a good idea to help streamline the
installation process of future editions of Visual Studio, and no personal information will be sent.
You can click the Next button at this screen after you have selected or cleared the check box
indicating whether or not you want this information sent.
4. The third step in the installation process is the license agreement. Read the license agreement
and then select the option button indicating your acceptance of the licensing terms. Then click
the Next button to continue.
5. As with most setup programs, you are presented with a choice of options to be installed
as shown in below Picture. The default installation installs the recommended product features as
determined by Microsoft. You have the option to choose the default installation, a full
installation, or to customize the installation. When choosing the custom installation feature, you
will be presented with a dialog box allowing you to choose the languages and features of each
language to be installed. If disk space allows, it is recommended that you choose a full
installation. However, if you choose to customize the installation and omit some features from
being installed, you can always install those features later by rerunning the setup program.
After choosing your installation option, click the Install button to have those features installed.
6. The first component that is installed is the Microsoft .NET Framework version 3.5. During theinstallation of this component you will be required to restart your computer. After your computer has restarted and you log back in, the setup program will continue. Note to Windows
Vista users: you will be prompted that the setup program needs to run and will need to grant
permission to let the setup program continue. After the setup program continues, you can sit
back and relax while all of the features are being installed. The setup program can take anywhere from 20 minutes on up depending on the installation features chosen and the speed of
your computer.
7. Once the installation has been completed, you will be presented with a dialog box informing
you of the status of the installation. Here you can see any problems that the setup program
encountered. At this point you are encouraged to update your computer with the latest security
patches and a link is provided in the notes to Windows Update. When you have finished
reviewing the setup status, click the Finish button to move on to the next step.
8. If you chose to have your setup information sent to Microsoft, the next step will be a dialog
box sending the setup information. This dialog box requires no action on your part and it will
automatically close when finished. The next dialog box is the one shown earlier in Figure 1
with the option to install the production documentation enabled. Click the Install Product
Documentation link to install the MSDN library.
9. The first step in installing the MSDN library is choosing whether to send the setup information to Microsoft. Make the appropriate choice and then click the Next button to continue.
Again, it is recommended to send this information to help streamline future MSDN library
installations.
10. Next, read and accept the license agreement. After you click the option button to accept the
license agreement, click the Next button to continue.
11. Like the installation of Visual Studio 2008, the MSDN library installation provides you with
the options to choose the installation that best suits your needs, as shown in Figure 3. If you
chose to install the complete Visual Studio 2008 product set then you’ll most likely want
to choose the full installation of the MSDN library. After making your installation option
choice, click the Install button to begin the installation.
If you have the spare hard drive space, it is a very good idea to install the full documentation. That wayyou have access to the full library, which will be important if you choose a limited set of options during
the install and later add more features.
12. After the MSDN documentation has been installed, you are presented with a dialog box informing you of the status of the installation. Click the Finish button to be returned to the initial setup screen again. The Check for Service Releases option is now available.
It is a good idea to select Service Releases to check for updates. Microsoft has done a good job of making software updates available through the Internet. These updates can include anything from additional documentation to bug fixes. You will be given the choice to install any updates through a Service Pack CD or the Internet. Obviously, the Internet option requires an active connection. Since updates can be quite large, a fast connection is highly recommended.
