Encoding.UTF8 Property
Microsoft Silverlight will reach end of support after October 2021. Learn more.
Updated: October 2010
Gets an encoding for the UTF-8 format.
Namespace: System.Text
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Shared ReadOnly Property UTF8 As Encoding
public static Encoding UTF8 { get; }
Property Value
Type: System.Text.Encoding
An encoding for the UTF-8 format.
Remarks
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 Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
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
outputBlock.Text &= String.Format("{0:X2} ", byt)
Next
outputBlock.Text &= vbCrLf
Dim value2 As String = enc.GetString(bytes, 0, bytes.Length)
outputBlock.Text &= value2 & vbCrLf
Catch e As EncoderFallbackException
outputBlock.Text += String.Format("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) & vbCrLf
End Try
End Sub
End Module
' The example displays the following output:
' Unable to encode U+D802 at index 2
using System;
using System.Text;
public class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
Encoding enc = new UTF8Encoding(true, true);
string value = "\u00C4 \uD802\u0033 \u00AE";
try
{
byte[] bytes = enc.GetBytes(value);
foreach (var byt in bytes)
outputBlock.Text += String.Format("{0:X2} ", byt);
outputBlock.Text += "\n";
string value2 = enc.GetString(bytes, 0, bytes.Length);
outputBlock.Text += value2 + "\n";
}
catch (EncoderFallbackException e)
{
outputBlock.Text += String.Format("Unable to encode {0} at index {1}",
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) + "\n";
}
}
}
// The example displays the following output:
// Unable to encode U+D802 at index 2
Examples
The following code example determines the number of bytes required to encode a character array, encodes the characters, and displays the resulting bytes.
Imports System.Text
Public Class Example
Private Shared outputBlock As System.Windows.Controls.TextBlock
Public Shared Sub Demo(ByVal outBlock As System.Windows.Controls.TextBlock)
outputBlock = outBlock
' 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(&H306), ChrW(&H1FD), ChrW(&H3B2), ChrW(&HD8FF), ChrW(&HDCFF)}
' Get different encodings.
Dim u8 As Encoding = Encoding.UTF8
Dim u16LE As Encoding = Encoding.Unicode
Dim u16BE As Encoding = Encoding.BigEndianUnicode
' Encode the entire array, and print out the counts and the resulting bytes.
PrintCountsAndBytes(myChars, u8)
PrintCountsAndBytes(myChars, u16LE)
PrintCountsAndBytes(myChars, u16BE)
End Sub
Public Shared Sub PrintCountsAndBytes(ByVal chars() As Char, ByVal enc As Encoding)
' Display the name of the encoding used.
outputBlock.Text += String.Format("{0,-30} :", enc.ToString())
' Display the exact byte count.
Dim iBC As Integer = enc.GetByteCount(chars)
outputBlock.Text += String.Format(" {0,-3}", iBC)
' Display the maximum byte count.
Dim iMBC As Integer = enc.GetMaxByteCount(chars.Length)
outputBlock.Text += String.Format(" {0,-3} :", iMBC)
' Encode the array of chars.
Dim bytes As Byte() = enc.GetBytes(chars)
' Display all the encoded bytes.
PrintHexBytes(bytes)
End Sub
Public Shared Sub PrintHexBytes(ByVal bytes() As Byte)
If bytes Is Nothing OrElse bytes.Length = 0 Then
outputBlock.Text &= "<none>" & vbCrLf
Else
Dim i As Integer
For i = 0 To bytes.Length - 1
outputBlock.Text += String.Format("{0:X2} ", bytes(i))
Next i
outputBlock.Text &= vbCrLf
End If
End Sub
End Class
' This example produces the following output.
' 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
using System;
using System.Text;
public class Example
{
private static System.Windows.Controls.TextBlock outputBlock;
public static void Demo(System.Windows.Controls.TextBlock outBlock)
{
outputBlock = outBlock;
// 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)
char[] myChars = new char[] { 'z', 'a', '\u0306', '\u01FD', '\u03B2', '\uD8FF', '\uDCFF' };
// Get different encodings.
Encoding u8 = Encoding.UTF8;
Encoding u16LE = Encoding.Unicode;
Encoding u16BE = Encoding.BigEndianUnicode;
// Encode the entire array, and print out the counts and the resulting bytes.
PrintCountsAndBytes(myChars, u8);
PrintCountsAndBytes(myChars, u16LE);
PrintCountsAndBytes(myChars, u16BE);
}
public static void PrintCountsAndBytes(char[] chars, Encoding enc)
{
// Display the name of the encoding used.
outputBlock.Text += String.Format("{0,-30} :", enc.ToString());
// Display the exact byte count.
int iBC = enc.GetByteCount(chars);
outputBlock.Text += String.Format(" {0,-3}", iBC);
// Display the maximum byte count.
int iMBC = enc.GetMaxByteCount(chars.Length);
outputBlock.Text += String.Format(" {0,-3} :", iMBC);
// Encode the array of chars.
byte[] bytes = enc.GetBytes(chars);
// Display all the encoded bytes.
PrintHexBytes(bytes);
}
public static void PrintHexBytes(byte[] bytes)
{
if ((bytes == null) || (bytes.Length == 0))
outputBlock.Text += "<none>" + "\n";
else
{
for (int i = 0; i < bytes.Length; i++)
outputBlock.Text += String.Format("{0:X2} ", bytes[i]);
outputBlock.Text += "\n";
}
}
}
/*
This code produces the following output.
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
*/
Version Information
Silverlight
Supported in: 5, 4, 3
Silverlight for Windows Phone
Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0
XNA Framework
Supported in: Xbox 360, Windows Phone OS 7.0
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.
See Also
Reference
Other Resources
Change History
Date |
History |
Reason |
|---|---|---|
October 2010 |
Noted replacement fallback behavior. |
Customer feedback. |