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Encoding.UTF8 Property

Gets an encoding for the UTF-8 format.

Namespace:  System.Text
Assembly:  mscorlib (in mscorlib.dll)

'Declaration
Public Shared ReadOnly Property UTF8 As Encoding

Property Value

Type: System.Text.Encoding
An encoding for the UTF-8 format.

This property returns a UTF8Encoding object that encodes Unicode (UTF-16-encoded) characters into a sequence of one to four bytes per character, and that decodes a UTF-8-encoded byte array to Unicode (UTF-16-encoded) characters. For information about the character encodings supported by the .NET Framework and a discussion of which Unicode encoding to use, see Character Encoding in the .NET Framework.

The UTF8Encoding object that is returned by this property might not have the appropriate behavior for your application.

  • It returns a UTF8Encoding object that provides a Unicode byte order mark (BOM). To instantiate a UTF8 encoding that doesn't provide a BOM, call any overload of the UTF8Encoding constructor.

  • It returns a UTF8Encoding object that uses replacement fallback to replace each string that it can't encode and each byte that it can't decode with a question mark ("?") character. Instead, you can call the UTF8Encoding.UTF8Encoding(Boolean, Boolean) constructor to instantiate a UTF8Encoding object whose fallback is either an EncoderFallbackException or a DecoderFallbackException, as the following example illustrates.

    Imports System.Text
    
    Module Example
       Public Sub Main()
          Dim enc As Encoding = New UTF8Encoding(True, True)
          Dim value As String = String.Format("{0} {1}{2} {3}", 
                                ChrW(&h00C4), ChrW(&hD802), ChrW(&h0033), ChrW(&h00AE))
    
          Try 
             Dim bytes() As Byte = enc.GetBytes(value)
             For Each byt As Byte In bytes
                Console.Write("{0:X2} ", byt)
             Next       
             Console.WriteLine()
             Dim value2 As String = enc.GetString(bytes)
             Console.WriteLine(value2)
          Catch e As EncoderFallbackException
             Console.WriteLine("Unable to encode {0} at index {1}", 
                               If(e.IsUnknownSurrogate(), 
                                  String.Format("U+{0:X4} U+{1:X4}", 
                                                Convert.ToUInt16(e.CharUnknownHigh),
                                                Convert.ToUInt16(e.CharUnknownLow)),
                                  String.Format("U+{0:X4}", 
                                                Convert.ToUInt16(e.CharUnknown))),
                               e.Index)
          End Try 
       End Sub 
    End Module 
    ' The example displays the following output: 
    '       Unable to encode U+D802 at index 2
    

The following example determines the number of bytes required to encode a character array, encodes the characters, and displays the resulting bytes.

Imports System
Imports System.Text
Imports Microsoft.VisualBasic

Public Class SamplesEncoding   

   Public Shared Sub Main()

      ' The characters to encode: 
      '    Latin Small Letter Z (U+007A) 
      '    Latin Small Letter A (U+0061) 
      '    Combining Breve (U+0306) 
      '    Latin Small Letter AE With Acute (U+01FD) 
      '    Greek Small Letter Beta (U+03B2) 
      '    a high-surrogate value (U+D8FF) 
      '    a low-surrogate value (U+DCFF) 
      Dim myChars() As Char = {"z"c, "a"c, ChrW(&H0306), ChrW(&H01FD), ChrW(&H03B2), ChrW(&HD8FF), ChrW(&HDCFF)}


      ' Get different encodings. 
      Dim u7 As Encoding = Encoding.UTF7
      Dim u8 As Encoding = Encoding.UTF8
      Dim u16LE As Encoding = Encoding.Unicode
      Dim u16BE As Encoding = Encoding.BigEndianUnicode
      Dim u32 As Encoding = Encoding.UTF32

      ' Encode the entire array, and print out the counts and the resulting bytes.
      PrintCountsAndBytes(myChars, u7)
      PrintCountsAndBytes(myChars, u8)
      PrintCountsAndBytes(myChars, u16LE)
      PrintCountsAndBytes(myChars, u16BE)
      PrintCountsAndBytes(myChars, u32)

   End Sub 'Main


   Public Shared Sub PrintCountsAndBytes(chars() As Char, enc As Encoding)

      ' Display the name of the encoding used.
      Console.Write("{0,-30} :", enc.ToString())

      ' Display the exact byte count. 
      Dim iBC As Integer = enc.GetByteCount(chars)
      Console.Write(" {0,-3}", iBC)

      ' Display the maximum byte count. 
      Dim iMBC As Integer = enc.GetMaxByteCount(chars.Length)
      Console.Write(" {0,-3} :", iMBC)

      ' Encode the array of chars. 
      Dim bytes As Byte() = enc.GetBytes(chars)

      ' Display all the encoded bytes.
      PrintHexBytes(bytes)

   End Sub 'PrintCountsAndBytes


   Public Shared Sub PrintHexBytes(bytes() As Byte)

      If bytes Is Nothing OrElse bytes.Length = 0 Then
         Console.WriteLine("<none>")
      Else 
         Dim i As Integer 
         For i = 0 To bytes.Length - 1
            Console.Write("{0:X2} ", bytes(i))
         Next i
         Console.WriteLine()
      End If 

   End Sub 'PrintHexBytes 

End Class 'SamplesEncoding


'This code produces the following output. 

'System.Text.UTF7Encoding       : 18  23  :7A 61 2B 41 77 59 42 2F 51 4F 79 32 50 2F 63 2F 77 2D 
'System.Text.UTF8Encoding       : 12  24  :7A 61 CC 86 C7 BD CE B2 F1 8F B3 BF 
'System.Text.UnicodeEncoding    : 14  16  :7A 00 61 00 06 03 FD 01 B2 03 FF D8 FF DC 
'System.Text.UnicodeEncoding    : 14  16  :00 7A 00 61 03 06 01 FD 03 B2 D8 FF DC FF 
'System.Text.UTF32Encoding      : 24  32  :7A 00 00 00 61 00 00 00 06 03 00 00 FD 01 00 00 B2 03 00 00 FF FC 04 00

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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