String manipulation is an important part of
programming because it helps to process data that come in the form of non-numeric
types such as name, address, gender, city, book title and more.8.1 String Manipulation
Using + and & signs.
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" and "Basic" into "Visual Basic" using
"Visual"&"Basic" or "Visual "+"Basic",
as shown in the example below
Example 8.1
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
Dim text1, text2, text3 As String
text1 = "Visual"
text2 = "Basic"
text3 = text1 + text2
Label1.Text = text3
End Sub
End Class
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The line text3=text1+ text2 can be replaced by
text3=text1 & text2 and produced 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 8.2
Dim text1, text3 as string
Dim Text2 As Integer
text1 = "Visual"
text2=22
text3=text1+text2
Label1.Text = text3
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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 strings, 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 = " 2008"
text6 = text1 + text2 + text3+text4+Text5
Label1.Text = text6
End Sub
End Class
Running the above program
will produce the following screen shot.
8.2
String Manipulation Using VB2008 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 VB2008 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 length function returns an integer
value which is the length of a phrase or a sentence, including the empty
spaces. The format 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:
The Right function extracts the right portion of a phrase.
The format for Visual Basic 6 is
Right
(“Phrase”, n)
Where n is the starting position from the right of the
phase where the portion of the phrase is going to be extracted. For
example,
Right(“Visual
Basic”, 4) = asic
However, this format is not applicable in VB2008.
In VB2008, we need use the following format
Microsoft.VisualBasic.Right("Phrase",n)
Example 8.3
Private Sub Button1_Click(ByVal
sender As System.Object, ByVal e As System.EventArgs) Handles
Button1.Click
Dim text1 As String
text1 = TextBox1.Text
Label1.Text = Microsoft.VisualBasic.Right(text1, 4)
End Sub
The above program will return four right most
characters of the phrase entered into the textbox.
The Output
*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 VB2008.
The Left function extract the left portion of a phrase.
The format 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
.
I Other functions will be
discussed in future lessons.
