VB.Net Tutorial/Data Type/String Functions

CStr: Convert Double to String

Public Class Tester
    Public Shared Sub Main
    
    Dim x As Double
    x = 12345678901234567890D
    Console.WriteLine(CStr(x))

    End Sub
End Class

1.23456789012346E+19

Duplicate a string

Public Class Tester
    Public Shared Sub Main
       Console.WriteLine(StrDup(30, "-"))
        
    End Sub

End Class

------------------------------

Format: c

Public Class Tester
    Public Shared Sub Main
    
    
      Console.WriteLine( Format(123, "c") )
    End Sub
End Class

$123.00

Get string index by using InStr

Class Tester
     Shared Sub Main()
        Dim userInput As String
        userInput = "  asdf  "
        Console.WriteLine(InStr(userInput, "f"))
     End Sub
End Class

6

Instr

Public Class Tester
    Public Shared Sub Main
    Dim MyString As String, YourString As String
    MyString = "asdf"
    YourString = "fdsa"    
    
        Console.WriteLine(InStr(2, MyString, YourString))
    End Sub
End Class

0

Instr: find character in a string

Module Tester
    Public Sub Main()
        Dim sHello As String = "Hello World"
        Console.WriteLine("Original string: {0}", sHello)
        Console.WriteLine("Find character (Instr(1, sHello, "l")) : {0}", InStr(1, sHello, "l"))
    End Sub
End Module

Original string: Hello World
Find character (Instr(1, sHello, "l")) : 3

Instr: find sub string a in a string

Module Tester
    Public Sub Main()
        Dim sHello As String = "Hello World"
        Console.WriteLine("Original string: {0}", sHello)
        Console.WriteLine("Find substring (Instr(1, sHello, "World")) : {0}", InStr(1, sHello, "Wor
ld"))
    End Sub
End Module

Original string: Hello World
Find substring (Instr(1, sHello, "World")) : 7

IsDBNull

Public Module modMain
   Public Sub Main()
      Dim title As String = "Mr."
      Dim name As Object = DBNull.Value
      Dim addressLine1 As String = title & " " & name
      If IsDBNull(addressLine1) Then
         Console.WriteLine("Null value")
      Else
         Console.WriteLine(addressLine1)
      End If
   End Sub
End Module

Mr.

IsNumeric, IsDate, IsNothing

Public Class Tester
    Public Shared Sub Main
        Dim theData As String = Nothing
        Dim result As New System.Text.StringBuilder
        " ----- Format nothing.
        result.AppendLine(String.Format( _
           "IsNumeric({0}) ... {1}", theData, IsNumeric(theData)))
        result.AppendLine(String.Format( _
           "IsDate({0}) ... {1}", theData, IsDate(theData)))
        result.AppendLine(String.Format( _
           "IsNothing({0}) ... {1}", theData, IsNothing(theData)))
        result.AppendLine()
        " ----- Format a number in a string.
        theData = "-12.345"
        result.AppendLine(String.Format( _
           "IsNumeric({0}) ... {1}", theData, IsNumeric(theData)))
        result.AppendLine(String.Format( _
           "IsDate({0}) ... {1}", theData, IsDate(theData)))
        result.AppendLine(String.Format( _
           "IsNothing({0}) ... {1}", theData, IsNothing(theData)))
        result.AppendLine()
        " ----- Format a date in a string.
        theData = "July 17, 2007"
        result.AppendLine(String.Format( _
           "IsNumeric({0}) ... {1}", theData, IsNumeric(theData)))
        result.AppendLine(String.Format( _
           "IsDate({0}) ... {1}", theData, IsDate(theData)))
        result.Append(String.Format( _
           "IsNothing({0}) ... {1}", theData, IsNothing(theData)))
        Console.WriteLine(result.ToString())
    End Sub
End Class

IsNumeric() ... False
IsDate() ... False
IsNothing() ... True
IsNumeric(-12.345) ... True
IsDate(-12.345) ... False
IsNothing(-12.345) ... False
IsNumeric(July 17, 2007) ... False
IsDate(July 17, 2007) ... True
IsNothing(July 17, 2007) ... False

LCase: change string to lower case

Module Tester
    Public Sub Main()
        Dim sHello As String = "Hello World"
        Console.WriteLine("Original string: {0}", sHello)
        Console.WriteLine("Lowercase (LCase(sHello)) : {0}", LCase(sHello))
    End Sub
End Module

Original string: Hello World
Lowercase (LCase(sHello)) : hello world

Left: get characters from left

Module Tester
    Public Sub Main()
        Dim sHello As String = "Hello World"
        Console.WriteLine("Original string: {0}", sHello)
        Console.WriteLine("Leftmost two characters (Left(sHello, 2)): {0}", Left(sHello, 2))
    End Sub
End Module

Original string: Hello World
Leftmost two characters (Left(sHello, 2)): He

Len: get string length

Public Class Tester
    Public Shared Sub Main
    
    
        Console.WriteLine(Len("txtString1.Text"))
    End Sub
End Class

15

Microsoft.VisualBasic.Left

public class Test
   public Shared Sub Main
        Dim strName As String = "Visual Basic Express"
        If Microsoft.VisualBasic.Left(strName, 3) = "Vis" Then Console.WriteLine("True")
        If strName.StartsWith("Vis") Then Console.WriteLine("True")
   End Sub
   
End class

True
True

Mid(string, 4, 5): get sub string from middle

Module Tester
    Public Sub Main()
        Dim sHello As String = "Hello World"
        Console.WriteLine("Original string: {0}", sHello)
        Console.WriteLine("From middle of string (Mid(sHello, 4, 5)): {0}", Mid(sHello, 4, 5))
    End Sub
End Module

Original string: Hello World
From middle of string (Mid(sHello, 4, 5)): lo Wo

Mid(string, 7): get sub string from start

Module Tester
    Public Sub Main()
        Dim sHello As String = "Hello World"
        Console.WriteLine("Original string: {0}", sHello)
        Console.WriteLine("Starting with character (Mid(sHello, 7)): {0}", Mid(sHello, 7))
    End Sub
End Module

Original string: Hello World
Starting with character (Mid(sHello, 7)): World

Passing formatted numeric values to Val

Option Strict On
Public Module Tester
   Public Sub Main()
      " Passing formatted numeric values to Val
      Console.WriteLine(Val("$1034.51"))       
      Console.WriteLine(Val("1,032.54"))       
   End Sub
End Module

0
1

Passing String values to Val

Option Strict On
Public Module Tester
   Public Sub Main()
      " 
      Console.WriteLine(Val("913.3"))          
      Console.WriteLine(Val("131AC57"))        
      Console.WriteLine(Val("-132.23"))        
      Console.WriteLine(Val("+1203.22"))       
      Console.WriteLine(Val("A0545"))          
      Console.WriteLine()
   End Sub
End Module

913.3
131
-132.23
1203.22
0

Right: get characters from right

Module Tester
    Public Sub Main()
        Dim sHello As String = "Hello World"
        Console.WriteLine("Original string: {0}", sHello)
        Console.WriteLine("Rightmost four characters (Right(sHello, 4)): {0}", Right(sHello, 4))
    End Sub
End Module

Original string: Hello World
Rightmost four characters (Right(sHello, 4)): orld

String.Copy

public class Test
   public Shared Sub Main
        Dim str1, str2 As String
        str1 = "some text"
        str2 = str1
        str2 = String.Copy(str1)
        Console.WriteLine(str1 & vbCrLf & str2)
   End Sub
   
End class

some text
some text

String handling function: Len

Module Tester
    Public Sub Main()
        Dim sHello As String = "Hello World"
        Console.WriteLine("Original string: {0}", sHello)
        Console.WriteLine("Length of string (Len(sHello)): {0}", Len(sHello))
    End Sub
End Module

Original string: Hello World
Length of string (Len(sHello)): 11

UCase: change string to upper case

Module Tester
    Public Sub Main()
        Dim sHello As String = "Hello World"
        Console.WriteLine("Original string: {0}", sHello)
        Console.WriteLine("Uppercase (UCase(sHello)) : {0}", UCase(sHello))
    End Sub
End Module

Original string: Hello World
Uppercase (UCase(sHello)) : HELLO WORLD

Use String.Concat to concatenate two strings

public class Test
   public Shared Sub Main
        Dim aryStrings() As String = {"string1", "string2", "string3", "string4"}
        Dim strLongString As String
        strLongString = String.Concat(aryStrings)
        Console.WriteLine(strLongString)
   End Sub
   
End class

string1string2string3string4