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We have learned about the basic
concept of function as well as the MsgBox and InputBox functions in
Lesson 12. I. In fact, I have already shown you a few string
manipulation functions in Lesson 8, they are the Len function, the Left
function and the Right Function. In this lesson, we will learn other
string manipulation functions.
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13.1 The Mid Function
The Mid function is used to retrieve a part of text form a given phrase. The syntax of the Mid
Function is
Mid(phrase, position,n)
where
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phrase is the string
from which a part of text is to be retrieved.
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position is the starting
position of the phrase from which the retrieving process begins.
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n is the number of
characters to retrieve.
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Example
13.1:
Private Sub
Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
Handles Button1.Click
Dim myPhrase As String
myPhrase = Microsoft.VisualBasic.InputBox("Enter your phrase")
Label1.Text = Mid(myPhrase, 2, 6)
End Sub
* In this example, when a user clicks the command button, an input box will pop up
asking the user to input a phrase. After a phrase is entered and the OK button
is pressed, the label will show the extracted text starting from position 2 of
the phrase and the number of characters extracted is 6. The diagrams are shown
below:
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13.2 The Right Function
The
Right function extracts the right portion of a
phrase. The syntax is
Microsoft.Visualbasic.Right (ˇ°Phraseˇ±, 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:
Microsoft.Visualbasic.Right
(ˇ°Visual Basicˇ±, 4) = asic
Example 13.2: The following code extracts the right portion any phrase
entered by the user.
Private Sub Button1_Click (ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
Dim myword As String
myword = TextBox1.Text
Label1.Text = Microsoft.VisualBasic.Right
(myword, 4)
End Sub
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13.3 The Left Function
The
Left function extracts the left portion of a
phrase. The syntax is
Microsoft.Visualbasic.Right (ˇ°Phraseˇ±, 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(ˇ°Visual Basicˇ±, 4) =
asic
Example 13.3: The following code extracts the left portion any phrase
entered by the user.
Private Sub Button1_Click (ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
Dim myword As String
myword = TextBox1.Text
Label1.Text = Microsoft.VisualBasic.Left
(myword, 4)
End Sub
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13.4 The Trim Function
The Trim function trims the empty spaces on both side of the phrase. The syntax is
Trim(ˇ°Phraseˇ±)
.For example,
Trim (ˇ° Visual Basic ˇ±) = Visual basic
Example 13.4
Private Sub Button1_Click(ByVal sender As
System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim myPhrase As String
myPhrase = Microsoft.VisualBasic.InputBox("Enter your phrase")
Label1.Text = Trim(myPhrase)
End Sub
13.5 The Ltrim Function
The Ltrim function trims the empty spaces of the left portion of the phrase. The syntax is
Ltrim(ˇ°Phraseˇ±)
.For example,
Ltrim
(ˇ° Visual Basicˇ±)= Visual basic
13.6 The Rtrim Function
The Rtrim function trims the empty spaces of the right portion of the phrase. The syntax is
Rtrim(ˇ°Phraseˇ±)
.For example,
Rtrim (ˇ°Visual Basic ˇ±) = Visual Basic
13.7
The InStr
function
The InStr function looks for a phrase that is embedded within the original phrase and returns the starting position of the embedded phrase. The syntax is
Instr (n, original phase, embedded phrase)
Where n is the position where the Instr
function will begin to look for the embedded phrase. For example
Instr(1, ˇ°Visual Basicˇ±,ˇ± Basicˇ±)=8
*The function returns a numeric value.
You can write a program code as shown below:
Private Sub Button1_Click(ByVal sender As
System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Label1.Text = InStr(1, "Visual Basic", "Basic")
End Sub
13.8 The Ucase and the Lcase Functions
The Ucase function converts all the characters of a string to
capital letters. On the other hand, the Lcase function converts all the
characters of a string to small letters.
The syntax is
Microsoft.VisualBasic.UCase(Phrase)
Microsoft.VisualBasic.LCase(Phrase)
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For example,
Microsoft.VisualBasic.Ucase(ˇ°Visual
Basicˇ±) =VISUAL BASIC
Microsoft.VisualBasic.Lcase(ˇ°Visual
Basicˇ±) =visual basic
13.9 The Chr and the Asc
functions
The Chr function returns
the string that corresponds to an ASCII code while the Asc function
converts an ASCII character or symbol to the corresponding ASCII code. ASCII
stands for ˇ°American Standard Code for Insyntaxion Interchangeˇ±. Altogether
there are 255 ASCII codes and as many ASCII characters. Some of the characters
may not be displayed as they may represent some actions such as the pressing of
a key or produce a beep sound. The syntax of the Chr function is
Chr(charcode)
and the syntax of the Asc function
is
Asc(Character)
The following are some examples:
Chr(65)=A, Chr(122)=z, Chr(37)=% ,
Asc(ˇ°Bˇ±)=66, Asc(ˇ°&ˇ±)=38
sage box. The
Style Value will determine what type of command buttons appear on the
message box, please refer Table 10.1 for types of command button displayed. The
Title argument will display the title of the message board.
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