The complete Reference - Visual Basic.net

Book Description
Master this massive programming language upgrade that raises Visual Basic functionality to the level of the .NET platform. Coverage includes all core topics--plus security, debugging, and helpful information on migrating existing Visual Basic projects to Visual Basic.NET.

The Definitive Resource on Visual Basic .NET

Take full advantage of all the new features of Visual Basic .NET with help from this comprehensive resource. Inside, you'll find in-depth information on the new object-oriented capabilities of Visual Basic .NET and details on the core language, including grammar, control-flow, operators, value-types, classes, interfaces, data structures and collections, delegates, GUI components, threading, and debugging. You'll refer to the extensive details inside this all-inclusive volume regularly as you program with Visual Basic .NET.
*Program against the .NET Framework's common language runtime and managed-execution environment
*Build value types and enumerators for industrial-strength code
*Design and implement class hierarchies with inheritance
*Use interfaces for sophisticated algorithms
*Program with Structured Exception Handling (SEH) to create stable applications
*Implement and deploy arrays, linked lists, trees, and other collections
*Use delegates and proven software industry patterns to create highly reusable and adaptable code
*Program against the .NET event and thread models
*Build enterprise business objects and easy-to-maintain flyweight user interfaces
*Learn how COM and .NET objects interoperate

Product Details

• Paperback: 901 pages
• Publisher: Osborne/McGraw-Hill (April 4, 2002)
• Language: English
• ISBN-10: 0072133813
• ISBN-13: 978-0072133813

click here to download

How to find the size of a Directory

Working with files and
directories is one of my favorites! With the help of the namespace, System.IO we can parse through the entire hard disk of our
computer. The System.IO namespace has rich inbuilt
methods/functions for every common task that we need to do. With the help of
these functions, we can easily write code for:



Does this file exist?

What is the size of this file?

Delete this file

Get all files in this directory ... and so on.



But the said namespace or other namespace does not provide us with a function
which gives the directory size. One way to find the directory size of any
folder/directory is as follows:



1) Start from the directory/folder that we need to find the size

2) Find all files in the current directory

3) Loop through each file and find the size of
each file

4) Chances are, we may end up with sub-folders.

5) We also need to find the number of files in this sub-folder

6) Since this is a repeating process, we should have a recursive mechanism were
we will parse through the end (until no more sub-directories exists)



The following example consists of three functions. A) Public DirectorySize(ByVal strStartDirectory as String)

B) Private FindDirectorySize(ByVal
strCurrentDir As String)

C) Private Sub RecursiveParseDirectory(ByVal strDirectory As String)



Include all the three functions in aspx or codebehind page and invoke the function, DirectorySize. Pass the folder/directory name as an
argument to this method and it will return you the size of the directory. You
will also need to declare a global variable called: intDirectorySize
which is of type, Integer.

Dim intDirectorySize As Integer Public Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) ' For this example, I have used "." which represents the current directory lblMsg.Text = "Directory size is " & DirectorySize(".") End Sub Public Function DirectorySize(ByVal strStartDir As String) Dim strStartDirectory As String = Server.MapPath(strStartDir) FindDirectorySize(strStartDirectory) RecursiveParseDirectory(strStartDirectory) Return intDirectorySize End Function Private Sub RecursiveParseDirectory(ByVal strDirectory As String) Dim strTemp As String Dim arrSubDirectories() As String = Directory.GetDirectories(strDirectory) For Each strTemp In arrSubDirectories FindDirectorySize(strTemp) RecursiveParseDirectory(strTemp) Next End Sub Private Sub FindDirectorySize(ByVal strCurrentDir As String) Dim DI As DirectoryInfo = New DirectoryInfo(strCurrentDir) Dim arrFiles As Array = DI.GetFiles() Dim FI As FileInfo Dim intDirsize As Integer = 0 For Each FI In arrFiles intDirsize += FI.Length Next intDirectorySize += intDirsize End Sub

How to retrieve the properties of file uploaded by the user.

We have already known how to
upload the file in the server, in this program we will see How to retrieve the
properties of file uploaded by the user.

We can retrieve some of
the interesting and useful properties of the file that is uploaded to the
webserver. The PostedFile provides us with three important properties, such as
FileName, ContentType and ContentLength. In our previous example, we already
saw, how to use the property, FileName? Now, we will see, how to know the size
of the file uploaded, and how to know the contentType of the file uploaded.



The following line of code
retrieves the ContentType of the file uploaded.



lblFileContentType.Text = MyFile.PostedFile.ContentType



The following line of code
retrieves the Size of the file uploaded.



lblFileSize.Text = CStr(MyFile.PostedFile.ContentLength)

Now, we will see an example which uses this property.

Example: Uploading a File in ASP .NET

<html> <head> <script language="VB" runat="server"> Sub Upload(Source As Object, e As EventArgs) If Not (myFile.PostedFile Is Nothing) Then Dim intFileNameLength as Integer Dim strFileNamePath as String Dim strFileNameOnly as String 'Logic to find the FileName (excluding the path) strFileNamePath = MyFile.PostedFile.FileName intFileNameLength = Instr(1, StrReverse(strFileNamePath), "\") strFileNameOnly = Mid(strFileNamePath, (Len(strFileNamePath)-intFileNameLength)+2) myFile.PostedFile.SaveAs("c:\inetpub\wwwroot\yourwebapp\upload\" & strFileNameOnly) lblMsg.Text = "File Upload Success." lblFileContentType.Text = "Content type: " & MyFile.PostedFile.ContentType lblFileSize.Text = "File size: " & CStr(MyFile.PostedFile.ContentLength) & " bytes" End If End Sub </script> </head> <body> <h3>File Upload</h3> <form enctype="multipart/form-data" runat="server"> File: <input id="myFile" type="file" runat="server"> <input type=button value="Upload" OnServerClick="Upload" runat="server"> <asp:label id=lblMsg runat="server" /> <asp:label id=lblFileContentType runat="server" /> <asp:label id=lblFileSize runat="server" /> </form> </body> </html>

Test this Script

How to control the size of file
uploaded to the web server?

While uploading a file to
the web server, we have a limit of 4MB by default. We can either decrease or
increase this value. The value is set in the key, maxRequestLength of machine
config file.



There is a maxRequestLength limit in the machine.config file (look for the
<system.web> section); in the http Runtime settings that you need to
alter/raise if you want to accept anything larger than 4Mb. These are the
standard settings for the httpRuntime:



<httpRuntime executionTimeout="90" maxRequestLength="4096"

useFullyQualifiedRedirectUrl="false" minFreeThreads="8"

minLocalRequestFreeThreads="4"
appRequestQueueLimit="100"/>

Sending an email with asp

Sending email is a very common task in any
web application. In almost every web application (web site), their will at
least be an occasion to send email in any fashion. In classic ASP, we worked
with the CDONTS object to send emails from an ASP page. The SMTP Mail class in
ASP .NET provides properties and methods for sending messages using the
Collaboration Data Objects for Windows 2000 (CDOSYS) message component In this
article, we will see, how can we send email from an ASP .NET page. In a nut
shell, today, we will be looking into the following:

• What we need to send Email
  from an ASP .NET?


• How to send an email from
  an ASP .NET page?


• What is new in sending
  email? (SmtpMail.SmtpServer)

What we need to send Email
from an ASP .NET?

The first thing that you need is the SMTP
service. SMTP service should be up and running. And you also need to import the
namespace, System.Web.Mail. To create a mail object, you need to create
an instance of MailMessage. MailMessage has all required properties such
as To, Subject, BCC, CC etc. For a complete list of method and properties, that
you can make use of, please visit

How to send an email from an
ASP .NET page?

<%@ Import Namespace="System.Web.Mail" %> <html> <script language="VB" runat="server"> Sub Page_Load(Sender As Object, E As EventArgs) Dim msg as New MailMessage() msg.To = "saurav@vb-tek.com" msg.From = "abhi@vb-tek.com" msg.Subject = "test" 'msg.BodyFormat = MailFormat.Html msg.BodyFormat = MailFormat.Text msg.Body = "hi" SmtpMail.SmtpServer = "localhost" SmtpMail.Send(msg) msg = Nothing lblMsg.Text = "An Email has been send to " & "das@silicomm.com" End Sub </script> <body style="font: 10pt verdana"> <form runat=server> <asp:Label id=lblMsg runat=Server /> </form> </body> </html>

In the above example, we
start the coding by importing the namespace, "System.Web.Mail". Then,
in the Page_Load event, we create an instance of MailMessage object. It is
through the MailMessage object, we set all the properties such as To, From,
Subject, Body etc. We can either send a text message or a html message. We need
to specify the bodyformat in the BodyFormat property. One we set all the
properties, it is ready to send the email. Before sending the email, you have
to set another important property, ie; SmtpServer. You have to set this
property. You should assign the name of your SMTP server to this property. In
most cases you can assign this as "localhost". If you do not set this
property, then you will not be able to send email from an ASP .NET page.
Finally we send the email using SmtpMail.Send. This method expects the
MailMessage as an argument. Actually the method Send is overloaded. You can
also send an email by specifiying, SmtpMail.Send (From, To, subject, body).

How to upload files in ASP .NET

Asking the user to upload
a file to the server is a very very common task in
most of the web applications. In classic ASP, uploading file was a very
difficult task, since we need a third party component or we need to write our
component to upload file from client to the server. In ASP .NET Uploading a file from client to the web server is so easy.
To be precise, we can get this done in two lines of code. Yes, two lines of
code. In this article, we will be looking into the following:

• How to Upload a file from
  Client to the Web server in ASP .NET?

First of all, we need a
HTML server control to allow the user to select the file. This is nothing but
the same old <input tag, with the type set to File, such as <input
type=file id=myFile runat=server
/>. This will give you the textbox and a browse button. Once you have
this, the user can select any file from their computer (or even from a
network). Then, in the Server side, we need the following line to save the file
to the Web Server.


myFile.PostedFile.SaveAs("DestinationPath")

Example: Uploading a File in ASP .NET

<html> <head> <script language="VB" runat="server"> Sub Upload(Source As Object, e As EventArgs) If Not (myFile.PostedFile Is Nothing) Then Dim intFileNameLength as Integer Dim strFileNamePath as String Dim strFileNameOnly as String 'Logic to find the FileName (excluding the path) strFileNamePath = MyFile.PostedFile.FileName intFileNameLength = Instr(1, StrReverse(strFileNamePath), "\") strFileNameOnly = Mid(strFileNamePath, (Len(strFileNamePath)-intFileNameLength)+2) myFile.PostedFile.SaveAs("c:\inetpub\wwwroot\yourwebapp\upload\" & strFileNameOnly) lblMsg.Text = "File Upload Success." End If End Sub </script> </head> <body> <h3>File Upload</h3> <form enctype="multipart/form-data" runat="server"> File: <input id="myFile" type="file" runat="server"> <asp:label id=lblMsg runat="server" /> <input type=button value="Upload" OnServerClick="Upload" runat="server"> </form> </body> </html>

In the above example, you
should note that, in the FORM tag, we have set the ectype to "multipart/form-data".
This is another important aspect while uploading a file to the web server. We
have a Input
tag which is of type file. Then we have a button called
"Upload". On the onclick of the button, you
can see that, we are using some string functions to find the FileName (excluding the path). Finally, we invoke the
method SaveAs
to save the file (upload) in the web server.

Simple Registry Editing

In this program we will show you how to work with registry.

this program is going to hide the turnoff option from the start menu

Just Copy and paste this simple code into your vb.net application and log off your computer and next log on having the same user account then will not be able to shutdown your computer.

In code window above the class Form1 write following line to import

Imports Mycrosoft.Win32

Then take a button and write down the following code into Button1_Click Subroutine

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)

Handles Button1.Click

Dim regvar As RegistryKey

Dim keyvalue As String

keyvalue = "Software\\Microsoft\\Windows\\CurrentVersion\\Policies\\Explorer"

regvar = Registry.CurrentUser.OpenSubKey(keyvalue, True)

regvar.SetValue("NoClose", 1)

Dim x As Integer = regvar.GetValue("NoClose")

End Sub

End Class

Solution: - If you want to get back your turnoff option just change the following line and run the vb.net program again.

regvar.SetValue("NoClose", 1) to

regvar.SetValue("NoClose", 0)

Make a simple browser

In this program a browser will be created and we will be able to be

Back, forward, refresh, stop, and go to homepage. The form will

Look as follow.

In code window above the class Form1 write following 4 lines to import

Imports System.IO

Imports System.Net

Imports System.Text

Imports System.Windows.Forms

Now double click the back button and write the following code in side button1_Click sub.

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

WebBrowser1.GoBack()

TextBox1.Text = WebBrowser1.Url.ToString()

End Sub

Now double click the Forward button and write the following code in side button2_Click sub

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click

WebBrowser1.GoForward()

TextBox1.Text = WebBrowser1.Url.ToString()

End Sub

Now double click the Stop button and write the following code in side button3_Click sub

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click

WebBrowser1.Stop()

End Sub

Now double click the Refresh button and write the following code in side button4_Click sub

Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click

WebBrowser1.Refresh()

End Sub

Now double click the home button and write the following code in side button5_Click sub

Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click

WebBrowser1.GoHome()

TextBox1.Text = WebBrowser1.Url.ToString()

End Sub

Now double click the form and write the following code in side from load Click sub

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

Button1.Enabled = False

Button2.Enabled = False

Button3.Enabled = False

End Sub

Now double click the web browser1 and choose from the Dropdown event to

“CanGoBackChanged”.

Now write the following code in sub

WebBrowser1_CanGoBackChanged

Private Sub WebBrowser1_CanGoBackChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles WebBrowser1.CanGoBackChanged

If WebBrowser1.CanGoBack = True Then

Button1.Enabled = True

Else

Button1.Enabled = False

End If

End Sub

Now do the same and create Sub WebBrowser1_CanGoForwardChanged

And write the following code inside the sub.

Private Sub WebBrowser1_CanGoForwardChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles WebBrowser1.CanGoForwardChanged

If WebBrowser1.CanGoForward = True Then

Button2.Enabled = True

Else

Button2.Enabled = False

End If

End Sub

Again do the same for the following sub WebBrowser1_DocumentCompleted

Private Sub WebBrowser1_DocumentCompleted(ByVal sender As System.Object, ByVal e As System.Windows.Forms.WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted

Button3.Enabled = False

End Sub

Again do the same for the following WebBrowser1_Navigated

Private Sub WebBrowser1_Navigated(ByVal sender As Object, ByVal e As System.Windows.Forms.WebBrowserNavigatedEventArgs) Handles WebBrowser1.Navigated

TextBox1.Text = WebBrowser1.Url.ToString()

Me.Text = WebBrowser1.DocumentTitle.ToString()

End Sub

Again do the same for the following WebBrowser1_Navigating

Private Sub WebBrowser1_Navigating(ByVal sender As Object, ByVal e As System.Windows.Forms.WebBrowserNavigatingEventArgs) Handles WebBrowser1.Navigating

Button3.Enabled = True

End Sub

End Class

Finally double click the go button and write the following code in side button6_Click sub

Private Sub Button6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button6.Click

WebBrowser1.Navigate(TextBox1.Text)

End Sub