VB .NET data types
There is no Variant data type in VB .NET. There are some other changes to
the traditional VB data types. A new Char type, which is an unsigned 16-bit
type, is used to store Unicode characters. The Decimal type is a 96-bit signed
Here are all the VB .NET data types:
Boolean System.Boolean 4 bytes True or False
Char System.Char 2 bytes 0–65535 (unsigned)
Byte System.Byte 1 byte 0–255 (unsigned)
Object System.Object 4 bytes Any Type
Date System.DateTime 8 bytes 01-Jan-0001 to
31-Dec-9999
Double System.Double 8 bytes +/–1.797E308
Decimal System.Decimal 12 bytes 28 digits
Integer System.Int16 2 bytes –32,768 to 32,767
System.Int32 4 bytes +/–2.147E9
Long System.Int64 8 bytes +/–9.223E18
Single System.Single 4 bytes +/–3.402E38
String System.String CharacterCount 2 billion
* 2 (plus 10 bytes) characters
Data Type Size in Bytes Description Type Byte 1 8-bit unsigned integer System.Byte Char 2 16-bit Unicode characters System.Char Integer 4 32-bit signed integer System.Int32 Double 8 64-bit floating point variable System.Double Long 8 64-bit signed integer System.Int64 Short 2 16-bit signed integer System.Int16 Single 4 32-bit floating point variable System.Single String Varies Non-Numeric Type System.String Date 8 System.Date Boolean 2 Non-Numeric Type System.Boolean Object 4 Non-Numeric Type System.Object Decimal 16 128-bit floating point variable System.Decimal
Assume that the user clicked a button asking to search for some information. You then create and display a TextBox for the user to enter the search criteria,and you also put a labelabove it describing the TextBox’s purpose
Converting Data Types
VB .NET offers four ways to change one data type into another. The .ToString
method is designed to convert any numeric data type into a text string.
The second way to convert data is to use the traditional VB functions: CStr(),
CBool(), CByte(), CChar(), CShort(), CInt(), CLng(), CDate(), CDbl(),
CSng(), CDec(), and CObj(). Here is an example:
Dim s As String
Dim i As Integer = 1551
s = CStr(i)
MessageBox.Show(s)
The third way is to use the Convert method, like this:
Dim s As String
Dim i As Integer = 1551
s = Convert.ToString(i)
MessageBox.Show(s)
The fourth way uses the CType function, with this syntax:
Dim s As String
Dim i As Integer = 1551
s = CType(i, String)
MessageBox.Show(s)
Graphics features of vb.net
There are many other methods you can use with a graphics object besides the DrawRectangle and FillRectangle methods illustrated in this example. Use DrawEllipse to draw circles and other round objects, and also try DrawLine, DrawPolygon, and others. The four arguments at the end of this line of code describe the horizontal (12) and vertical (15) point on the form where the upper-left corner of your rectangle is located, and the width (36) and height (45) of the rectangle: grObj.FillRectangle(brushBlue, 12, 15, 36, 45) The PSet and Point commands, which allowed you to manipulate individual pixels in earlier versions of VB, can be simulated by using the SetPixel or GetPixel methods of the System.Drawing Bitmap class. You can create a solid graphic (a square, circle, and so on) by simply using a brush to fill the area, without first using a pen to draw an outline
==========================================================================
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
'create graphics object
Dim grObj As System.Drawing.Graphics
grObj = Me.CreateGraphics
'create a red pen
Dim penRed As New System.Drawing.Pen(System.Drawing.Color.PaleVioletRed)
'make it fairly wide
penRed.Width = 9
'draw a square
grObj.DrawRectangle(penRed, 12, 12, 45, 45)
'create a brush (to fill the square)
Dim brushBlue As System.Drawing.Brush
brushBlue = New SolidBrush(Color.DarkBlue)
grObj.FillRectangle(brushBlue, 12, 12, 45, 45)
End Sub
=========================================================================
Array Search and Sort Methods in vb.net
You can now have arrays search themselves or sort themselves. Here’s an example showing how to use both the sort and search methods of the Array object. The syntax for these two methods is as follows:
Array.Sort(myArray)
And
arrayIndex = Array.BinarySearch(myArray, “Name”)
To see this feature in action, put a Button and a TextBox control on a form and change the TextBox’s MultiLine property to True. Then enter the following
This function clears out the ListBox, displays the array in the ListBox,
and then displays the count (the total number of items in the ArrayList) in
with 10 elements indexed from X(0) up to X(9):
 | |
|---|---|
| Developer(s) | Qt Development Frameworks (formerly known as Trolltech) |
| Stable release | 4.5.3 / 2009-10-01 |
| Written in | C++ |
| Operating system | Cross-platform |
| Development status | Active |
| Type | Widget toolkit |
| License | GNU LGPL GNU GPL with Qt special exception Proprietary[1] |
| Website | qt.nokia.com |
Imports System.Text.RegularExpressions
You can remove the password you have set for a database. Once a password
is set, the choice in the Tools, Security menu choice becomes Unset
Database Password. You will be prompted for the password; it is case-sensitive.
After you remove the database password, anyone has access to the database.
Let's remove the database password you set for databasename.mdb
