Encoding.UTF8 Property
Updated: October 2010
Gets an encoding for the UTF-8 format.
Assembly: mscorlib (in mscorlib.dll)
This property returns a UTF8Encoding object that encodes Unicode characters into a sequence of one to four bytes per character, and that decodes a UTF-8-encoded byte array to Unicode characters. For information about the character encodings supported by the .NET Framework and a discussion of which Unicode encoding to use, see Understanding Encodings.
The UTF8Encoding object that is returned by this property may not have the appropriate behavior for your application. It uses replacement fallback to replace each string that it cannot encode and each byte that it cannot 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
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The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.