VB2017 VB2015 VB2013 VB2012 VB2010 VB2008 VB6 VB Sample Codes 中文VB About Us

Lesson 8 : String Manipulation


In Visual Basic 2012 , string manipulation is important because it helps to process data that come in the form of non-numeric types such as names, addresses, gender, cities, book titles and more.

8.1 String Manipulation Using + and & signs.

In Visual Basic 2012, strings can be manipulated using the & sign and the + sign, both perform the string concatenation which means combining two or more smaller strings into larger strings. For example, we can join "Visual" ,"Basic" and "2012" into "Visual Basic 2012" using "Visual"&"Basic" or "Visual "+"Basic", as shown in the Examples below

Example 8.1(a)

Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
	Dim text1, text2, text3, text4 As String
	text1 = "Visual"
	text2 = "Basic"
	text3="2012"
	text4 = text1 + text2+text3
	MsgBox(text4)
End Sub
End Class

The line text4=text1+ text2 + text3 can be replaced by text4=text1 & text2 &text3 and produces the same output. However, if one of the variables is declared as numeric data type, you cannot use the + sign, you can only use the & sign.

Example 8.1(b)

Dim text1, text3 as string
Dim Text2 As Integer

text1 = "Visual" text2=22 text3=text1+text2 Label1.Text = text3

This code will produce an error because of data mismatch.However, using & instead of + will be all right.

Dim text1, text3 as string
Dim Text2 As Integer
	text1 = "Visual"
	text2=22
	text3=text1 & text2
	Label1.Text = text3

You can combine more than two strings to form a larger string, like the following example:

Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
	Dim text1, text2, text3, text4, text5, text6 As String
	text1 = "Welcome"
	text2 = " to"
	text3 = " Visual"
	text4 = " Basic" 
	text5 = " 2012" 
	text6 = text1 + text2 + text3+text4+text5 
	Label1.Text = text6
 End Sub
 End Class
 

Running the above program will produce the following screen shot, as shown in Figure 8.1.

Visual Basic 2012

Figure 8.1

8.2 String Manipulation Using the Built-in Functions

A function is similar to a normal procedure but the main purpose of the function is to accept a certain input and return a value which is passed on to the main program to finish the execution.There are numerous string manipulation functions built into Visual Basic 2012 but I will only discuss a few here and will explain the rest of them in later lessons.

8.2 (a) The Len Function

The Len function returns an integer value which is the length of a phrase or a sentence, including the empty spaces. The syntax is

Len ("Phrase")

For example,

Len (Visual Basic) = 12 and Len ("welcome to VB tutorial") = 22

Example 8.3

Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
	Label1.Text = Len(TextBox1.Text)
End Sub
End Class

The output is shown in Figure 8.2

Figure 8.2

8.2(b) The Right Function

The Right function extracts the right portion of a phrase. The syntax is

Microsoft.VisualBasic.Right("Phrase",n)

Example 8.2(a)

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
	Dim text1 As String
	Label1.Text = Microsoft.VisualBasic.Right(text1, 4)
End Sub

The above program returns four right most characters of the phrase entered into the textbox.

The Output is shown in Figure 8.3

Visual Basic 2012
Figure 8.3

*The reason of using the full reference is because many objects have the Right properties so using Right on its own will make it ambiguous to Visual Basic 2012.

8.2(c)The Left Function

The Left function extracts the left portion of a phrase. The syntax is

Microsoft.VisualBasic.Left("Phrase",n)

Where n is the starting position from the left of the phase where the portion of the phrase is going to be extracted. For example,

Microsoft.VisualBasic.Left ("Visual Basic", 4) = Visu


❮ Previous Lesson Next Lesson ❯


Copyright©2008 Dr.Liew Voon Kiong. All rights reserved |Contact|Privacy Policy