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UnicodeEncoding Class

Represents a UTF-16 encoding of Unicode characters.

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

[SerializableAttribute] 
[ComVisibleAttribute(true)] 
public class UnicodeEncoding : Encoding
/** @attribute SerializableAttribute() */ 
/** @attribute ComVisibleAttribute(true) */ 
public class UnicodeEncoding extends Encoding
SerializableAttribute 
ComVisibleAttribute(true) 
public class UnicodeEncoding extends Encoding

Encoding is the process of transforming a set of Unicode characters into a sequence of bytes. Decoding is the reverse; it is the process of transforming a sequence of encoded bytes into a set of Unicode characters.

The Unicode Standard assigns a code point (a number) to each character in every supported script. A Unicode Transformation Format (UTF) is a way to encode that code point. The Unicode Standard version 3.2 uses the following UTFs:

  • UTF-8, which represents each code point as a sequence of one to four bytes.

  • UTF-16, which represents each code point as a sequence of one to two 16-bit integers.

  • UTF-32, which represents each code point as a 32-bit integer.

The GetByteCount method determines how many bytes result in encoding a set of Unicode characters, and the GetBytes method performs the actual encoding.

Likewise, the GetCharCount method determines how many characters result in decoding a sequence of bytes, and the GetChars and GetString methods perform the actual decoding.

The encoder can use the big-endian byte order (most significant byte first) or the little-endian byte order (least significant byte first). For example, the Latin Capital Letter A (code point U+0041) is serialized as follows (in hexadecimal):

  • Big-endian byte order: 00 41

  • Little-endian byte order: 41 00

Optionally, the UnicodeEncoding provides a preamble, which is an array of bytes that you can prefix to the sequence of bytes resulting from the encoding process. If the preamble contains a byte order mark (code point U+FEFF), it helps the decoder determine the byte order and the transformation format or UTF. The Unicode byte order mark is serialized as follows (in hexadecimal):

  • Big-endian byte order: FE FF

  • Little-endian byte order: FF FE

It is generally more efficient to store Unicode characters using the native byte order. For example, it is better to use the little-endian byte order on little-endian platforms, such as Intel machines.

The GetPreamble method returns an array of bytes containing the byte order mark. If this byte array is prefixed to an encoded stream, it helps the decoder to identify the encoding format used.

For more information on Unicode encoding, byte order, and the byte order mark, see The Unicode Standard at www.unicode.org.

NoteNote

To enable error detection and to make the class instance more secure, use the UnicodeEncoding constructor that takes a throwOnInvalidBytes parameter and set that parameter to true. With error detection, a method that detects an invalid sequence of characters or bytes throws an ArgumentException. Without error detection, no exception is thrown, and the invalid sequence is generally ignored.

UnicodeEncoding corresponds to the Windows code pages 1200 (little-endian byte order) and 1201 (big-endian byte order).

The following code example demonstrates how to encode the string of Unicode characters into a byte array, using UnicodeEncoding. The byte array is decoded back into a string to demonstrate that there is no loss of data.

using System;
using System.Text;

class UnicodeEncodingExample {
    public static void Main() {
        // The encoding.
        UnicodeEncoding unicode = new UnicodeEncoding();
        
        // Create a string that contains Unicode characters.
        String unicodeString =
            "This Unicode string contains two characters " +
            "with codes outside the traditional ASCII code range, " +
            "Pi (\u03a0) and Sigma (\u03a3).";
        Console.WriteLine("Original string:");
        Console.WriteLine(unicodeString);

        // Encode the string.
        Byte[] encodedBytes = unicode.GetBytes(unicodeString);
        Console.WriteLine();
        Console.WriteLine("Encoded bytes:");
        foreach (Byte b in encodedBytes) {
            Console.Write("[{0}]", b);
        }
        Console.WriteLine();
        
        // Decode bytes back to string.
        // Notice Pi and Sigma characters are still present.
        String decodedString = unicode.GetString(encodedBytes);
        Console.WriteLine();
        Console.WriteLine("Decoded bytes:");
        Console.WriteLine(decodedString);
    }
}

import System.*;
import System.Text.*;

class UnicodeEncodingExample
{
    public static void main(String[] args)
    {
        // The encoding.
        UnicodeEncoding unicode = new UnicodeEncoding();

        // Create a string that contains Unicode characters.
        String unicodeString = "This Unicode string contains two characters " 
            + "with codes outside the traditional ASCII code range, " 
            + "Pi (\u03a0) and Sigma (\u03a3).";
        Console.WriteLine("Original string:");
        Console.WriteLine(unicodeString);

        // Encode the string.
        ubyte encodedBytes[] = unicode.GetBytes(unicodeString);
        Console.WriteLine();
        Console.WriteLine("Encoded bytes:");
        for(int iCtr = 0; iCtr < encodedBytes.length; iCtr++) {
            ubyte b = encodedBytes[iCtr];
            Console.Write("[{0}]", String.valueOf(b));
        }
        Console.WriteLine();

        // Decode bytes back to string.
        // Notice Pi and Sigma characters are still present.
        String decodedString = unicode.GetString(encodedBytes);
        Console.WriteLine();
        Console.WriteLine("Decoded bytes:");
        Console.WriteLine(decodedString);
    } //main
} //UnicodeEncodingExample

System.Object
   System.Text.Encoding
    System.Text.UnicodeEncoding
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

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

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0
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