VB.Net Tutorial/Data Type/String Functions

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Версия от 15:54, 26 мая 2010; Admin (обсуждение | вклад) (1 версия)
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CStr: Convert Double to String

<source lang="vbnet">Public Class Tester 

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

   End Sub

End Class</source> 

1.23456789012346E+19

Duplicate a string

<source lang="vbnet">Public Class Tester 

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

End Class</source> 

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

Format: c

<source lang="vbnet">Public Class Tester 

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

End Class</source> 

$123.00

Get string index by using InStr

<source lang="vbnet">Class Tester 

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

End Class</source> 

6

Instr

<source lang="vbnet">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</source> 

0

Instr: find character in a string

<source lang="vbnet">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</source> 

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

Instr: find sub string a in a string

<source lang="vbnet">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</source> 

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

IsDBNull

<source lang="vbnet">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</source> 

Mr.

IsNumeric, IsDate, IsNothing

<source lang="vbnet">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</source> 

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

<source lang="vbnet">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</source> 

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

Left: get characters from left

<source lang="vbnet">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</source> 

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

Len: get string length

<source lang="vbnet">Public Class Tester 

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

End Class</source> 

15

Microsoft.VisualBasic.Left

<source lang="vbnet">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</source> 

True
True

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

<source lang="vbnet">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</source> 

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

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

<source lang="vbnet">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</source> 

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

Passing formatted numeric values to Val

<source lang="vbnet">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</source> 

0
1

Passing String values to Val

<source lang="vbnet">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</source> 

913.3
131
-132.23
1203.22
0

Right: get characters from right

<source lang="vbnet">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</source> 

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

String.Copy

<source lang="vbnet">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</source> 

some text
some text

String handling function: Len

<source lang="vbnet">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</source> 

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

UCase: change string to upper case

<source lang="vbnet">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</source> 

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

Use String.Concat to concatenate two strings

<source lang="vbnet">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</source> 

string1string2string3string4
Источник — «http://vbex.ru/index.php?title=VB.Net_Tutorial/Data_Type/String_Functions&oldid=3134»