Programming Tutorials

String Insert, index off & format in VB.net

By: Issac  

String is a basic data structure used to hold string values , the functions with string makes string handling a much easier exercise.The Insert() function in String Class will insert a String in a specified index in the String instance.

System.String.Insert(Integer ind, String str) as String 

Parameters: 
ind – symbolizes the index of the specified string to be inserted.
str – is the string to be inserted.

Returns: 
String - The result string.

Exceptions: 
System.ArgumentOutOfRangeException: startIndex is negative or greater than the length of this instance
System.ArgumentNullException : If the argument is null.

For ex:
"This is Test".Insert (8,"Insert ") returns "This is Insert Test"

Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles Button1.Click
Dim str As String = "This is VB.NET Test"
Dim insStr As String = "Insert "
Dim strRes As String = str.Insert(15, insStr)
MsgBox(strRes)
End Sub
End Class

When you un this code you will get the message box showing "This is VB.NET Insert Test"

The IndexOf method in String Class returns the index of the first occurrence of the specified substring.
System.String.IndexOf(String str) As Integer 

Parameters: 
str - The parameter string to check its occurrences

Returns: 
Integer - If the parameter String occurred as a substring in the specified String
It returns position of the first character of the substring .
If it does not occur as a substring, -1 is returned.

Exceptions: 
System.ArgumentNullException: If the Argument is null.

For ex:
"This is a test".IndexOf ("Test") returns 10
"This is a test".IndexOf ("vb") returns -1

Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles Button1.Click
Dim str As String
str = "VB.NET TOP 10 SITES"
MsgBox(str.IndexOf("SITES"))
End Sub
End Class
When you execute this program you will get the number 14 in the message box. That means the substring "SITES" occurred and start in the position 14.


VB.NET String Format method replaces the argument Object into a text equivalent System.String.
System.Format(ByVal format As String, ByVal arg0 As Object) As String 

Parameters: 
String format : The format String
The format String Syntax is like {indexNumber: formatCharacter}
Object arg0: The object to be formatted.

Returns: 
String : is the formatted String

Exceptions: 
System.ArgumentNullException : The format String is null.
System.FormatException : The format item in format is invalid.

The number indicating an argument to format is less than zero, or greater than or equal to the number of specified objects to format.

Currency : 
String.Format("{0:c}", 10) will return $10.00
The currency symbol ($) displayed depends on the global locale settings you have in your system.

Date : 
String.Format ("Today's date is {0:D}", DateTime.Now) 
Displays Today's date like: 01 January 2005 

Time : 
String.Format ("The current time is {0:T}", DateTime.Now) 
Displays Current Time Like: 11:13:01

Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles Button1.Click
Dim Num As Double
Num = 11.3456789
MsgBox("Formatted String " & String.Format("{0:n4}", Num))
End Sub
End Class
When you run this source code you will get "Formatted String 11.3456"

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