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Lesson 13 : String Functions


We have learned the basic concept of function in Visual Basic 2012. In particular, we have shown you how to use the MsgBox function and InputBox function in Lesson 12. In fact, we have already illustrated 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 in visual basic 2012.

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 phrase is the string from which a part of text is to be retrieved. position is the starting position of the phrase from which the retrieving process begins. n is the number of characters to retrieve.

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 the user clicks the command button, an inputbox will pop up asking the user to input a phrase, as shown in Figure 13.1.

visual basic 2012
Figure 13.1 The InputBox

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 as shown in Figure 13.2.

visual basic 2012
Figure 13.2 The Extracted Text

13.2 The Right Function

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

Microsoft.Visualbasic.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:

Microsoft.Visualbasic.Right ("Visual Basic", 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

13.3 The Left Function

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

Microsoft.Visualbasic.Right ("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) = 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

13.4 The Trim Function

The Trim function trims the empty spaces on both side of the phrase. The syntax is

Trim("Phrase")

For example

Trim (" Visual Basic ") = 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("Phrase")

For example,

Ltrim (" Visual Basic 2012")= Visual basic 2012

13.6 The Rtrim Function

The Rtrim function trims the empty spaces of the right portion of the phrase. The syntax is

Rtrim("Phrase")

For example,

Rtrim ("Visual Basic 2012 ") = Visual Basic 2012

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, "Visual Basic 2012 ","Basic")=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 syntaxes are
Microsoft.VisualBasic.UCase(Phrase)
Microsoft.VisualBasic.LCase(Phrase)

For example,

Microsoft.VisualBasic.Ucase("Visual Basic") =VISUAL BASIC>

Microsoft.VisualBasic.Lcase("Visual Basic") =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 "American Standard Code for Information Interchange". 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("B")=66, Asc("&")=38


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