Export (0) Print
Expand All

UnicodeEncoding Class

Represents a UTF-16 encoding of Unicode characters.

System.Object
  System.Text.Encoding
    System.Text.UnicodeEncoding

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

'Declaration
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public Class UnicodeEncoding _
	Inherits Encoding

The UnicodeEncoding type exposes the following members.

  NameDescription
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryUnicodeEncodingInitializes a new instance of the UnicodeEncoding class.
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryUnicodeEncoding(Boolean, Boolean)Initializes a new instance of the UnicodeEncoding class. Parameters specify whether to use the big endian byte order and whether to provide a Unicode byte order mark.
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryUnicodeEncoding(Boolean, Boolean, Boolean)Initializes a new instance of the UnicodeEncoding class. Parameters specify whether to use the big endian byte order, whether to provide a Unicode byte order mark, and whether to throw an exception when an invalid encoding is detected.
Top

  NameDescription
Public propertyBodyNameWhen overridden in a derived class, gets a name for the current encoding that can be used with mail agent body tags. (Inherited from Encoding.)
Public propertySupported by the XNA FrameworkCodePageWhen overridden in a derived class, gets the code page identifier of the current Encoding. (Inherited from Encoding.)
Public propertyDecoderFallbackGets or sets the DecoderFallback object for the current Encoding object. (Inherited from Encoding.)
Public propertyEncoderFallbackGets or sets the EncoderFallback object for the current Encoding object. (Inherited from Encoding.)
Public propertyEncodingNameWhen overridden in a derived class, gets the human-readable description of the current encoding. (Inherited from Encoding.)
Public propertyHeaderNameWhen overridden in a derived class, gets a name for the current encoding that can be used with mail agent header tags. (Inherited from Encoding.)
Public propertyIsBrowserDisplayWhen overridden in a derived class, gets a value indicating whether the current encoding can be used by browser clients for displaying content. (Inherited from Encoding.)
Public propertyIsBrowserSaveWhen overridden in a derived class, gets a value indicating whether the current encoding can be used by browser clients for saving content. (Inherited from Encoding.)
Public propertyIsMailNewsDisplayWhen overridden in a derived class, gets a value indicating whether the current encoding can be used by mail and news clients for displaying content. (Inherited from Encoding.)
Public propertyIsMailNewsSaveWhen overridden in a derived class, gets a value indicating whether the current encoding can be used by mail and news clients for saving content. (Inherited from Encoding.)
Public propertyIsReadOnlyWhen overridden in a derived class, gets a value indicating whether the current encoding is read-only. (Inherited from Encoding.)
Public propertyIsSingleByteWhen overridden in a derived class, gets a value indicating whether the current encoding uses single-byte code points. (Inherited from Encoding.)
Public propertySupported by the XNA FrameworkSupported by Portable Class LibraryWebNameWhen overridden in a derived class, gets the name registered with the Internet Assigned Numbers Authority (IANA) for the current encoding. (Inherited from Encoding.)
Public propertyWindowsCodePageWhen overridden in a derived class, gets the Windows operating system code page that most closely corresponds to the current encoding. (Inherited from Encoding.)
Top

  NameDescription
Public methodSupported by the XNA FrameworkCloneWhen overridden in a derived class, creates a shallow copy of the current Encoding object. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryEqualsDetermines whether the specified Object is equal to the current UnicodeEncoding object. (Overrides Encoding.Equals(Object).)
Protected methodSupported by the XNA FrameworkSupported by Portable Class LibraryFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetByteCount(Char())When overridden in a derived class, calculates the number of bytes produced by encoding all the characters in the specified character array. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetByteCount(String)Calculates the number of bytes produced by encoding the characters in the specified String. (Overrides Encoding.GetByteCount(String).)
Public methodGetByteCount(Char*, Int32)Calculates the number of bytes produced by encoding a set of characters starting at the specified character pointer. (Overrides Encoding.GetByteCount(Char*, Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetByteCount(Char(), Int32, Int32)Calculates the number of bytes produced by encoding a set of characters from the specified character array. (Overrides Encoding.GetByteCount(Char(), Int32, Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetBytes(Char())When overridden in a derived class, encodes all the characters in the specified character array into a sequence of bytes. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetBytes(String)When overridden in a derived class, encodes all the characters in the specified string into a sequence of bytes. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetBytes(Char(), Int32, Int32)When overridden in a derived class, encodes a set of characters from the specified character array into a sequence of bytes. (Inherited from Encoding.)
Public methodGetBytes(Char*, Int32, Byte*, Int32)Encodes a set of characters starting at the specified character pointer into a sequence of bytes that are stored starting at the specified byte pointer. (Overrides Encoding.GetBytes(Char*, Int32, Byte*, Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetBytes(Char(), Int32, Int32, Byte(), Int32)Encodes a set of characters from the specified character array into the specified byte array. (Overrides Encoding.GetBytes(Char(), Int32, Int32, Byte(), Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetBytes(String, Int32, Int32, Byte(), Int32)Encodes a set of characters from the specified String into the specified byte array. (Overrides Encoding.GetBytes(String, Int32, Int32, Byte(), Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetCharCount(Byte())When overridden in a derived class, calculates the number of characters produced by decoding all the bytes in the specified byte array. (Inherited from Encoding.)
Public methodGetCharCount(Byte*, Int32)Calculates the number of characters produced by decoding a sequence of bytes starting at the specified byte pointer. (Overrides Encoding.GetCharCount(Byte*, Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetCharCount(Byte(), Int32, Int32)Calculates the number of characters produced by decoding a sequence of bytes from the specified byte array. (Overrides Encoding.GetCharCount(Byte(), Int32, Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetChars(Byte())When overridden in a derived class, decodes all the bytes in the specified byte array into a set of characters. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetChars(Byte(), Int32, Int32)When overridden in a derived class, decodes a sequence of bytes from the specified byte array into a set of characters. (Inherited from Encoding.)
Public methodGetChars(Byte*, Int32, Char*, Int32)Decodes a sequence of bytes starting at the specified byte pointer into a set of characters that are stored starting at the specified character pointer. (Overrides Encoding.GetChars(Byte*, Int32, Char*, Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetChars(Byte(), Int32, Int32, Char(), Int32)Decodes a sequence of bytes from the specified byte array into the specified character array. (Overrides Encoding.GetChars(Byte(), Int32, Int32, Char(), Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetDecoderObtains a decoder that converts a UTF-16 encoded sequence of bytes into a sequence of Unicode characters. (Overrides Encoding.GetDecoder.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetEncoderObtains an encoder that converts a sequence of Unicode characters into a UTF-16 encoded sequence of bytes. (Overrides Encoding.GetEncoder.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetHashCodeReturns the hash code for the current instance. (Overrides Encoding.GetHashCode.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetMaxByteCountCalculates the maximum number of bytes produced by encoding the specified number of characters. (Overrides Encoding.GetMaxByteCount(Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetMaxCharCountCalculates the maximum number of characters produced by decoding the specified number of bytes. (Overrides Encoding.GetMaxCharCount(Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetPreambleReturns a Unicode byte order mark encoded in UTF-16 format, if the constructor for this instance requests a byte order mark. (Overrides Encoding.GetPreamble.)
Public methodGetString(Byte())When overridden in a derived class, decodes all the bytes in the specified byte array into a string. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetString(Byte(), Int32, Int32)Decodes a range of bytes from a byte array into a string. (Overrides Encoding.GetString(Byte(), Int32, Int32).)

In XNA Framework 3.0, this member is inherited from Encoding.GetString(Byte(), Int32, Int32).


In Portable Class Library Portable Class Library, this member is inherited from Encoding.GetString(Byte(), Int32, Int32).
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodIsAlwaysNormalizedGets a value indicating whether the current encoding is always normalized, using the default normalization form. (Inherited from Encoding.)
Public methodIsAlwaysNormalized(NormalizationForm)When overridden in a derived class, gets a value indicating whether the current encoding is always normalized, using the specified normalization form. (Inherited from Encoding.)
Protected methodSupported by the XNA FrameworkSupported by Portable Class LibraryMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryToStringReturns a string that represents the current object. (Inherited from Object.)
Top

  NameDescription
Public fieldStatic memberSupported by the XNA FrameworkCharSizeRepresents the Unicode version 2.0 character size in bytes. This field is a constant.
Top

Encoding is the process of transforming a set of Unicode characters into a sequence of bytes. Decoding 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 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.

NoteNote

The UTF-7 encoding supports certain protocols for which it is required, most often e-mail or newsgroup protocols. Since UTF-7 is not particularly secure or robust, it should generally not be used. UTF-8 should normally be preferred to UTF-7.

For more information about the UTFs and other encodings supported by System.Text, see Character Encoding in the .NET Framework and Using Unicode Encoding.

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.

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

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 00 00 41

  • Little endian byte order: 41 00 00 00

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 computers.

Optionally, the UnicodeEncoding object provides a preamble, which is an array of bytes that can be prefixed to the sequence of bytes resulting from the encoding process. If the preamble contains a byte order mark (BOM), it helps the decoder determine the byte order and the transformation format or UTF. The GetPreamble method retrieves an array of bytes that can include the BOM.

NoteNote

To enable error detection and to make the class instance more secure, the application should 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 a ArgumentException. Without error detection, no exception is thrown, and the invalid sequence is generally ignored.

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


Imports System
Imports System.Text
Imports Microsoft.VisualBasic.Strings

Class UnicodeEncodingExample

    Public Shared Sub Main()
        ' The encoding.
        Dim uni As New UnicodeEncoding()

        ' Create a string that contains Unicode characters.
        Dim unicodeString As String = _
            "This Unicode string contains two characters " & _
            "with codes outside the traditional ASCII code range, " & _
            "Pi (" & ChrW(928) & ") and Sigma (" & ChrW(931) & ")."
        Console.WriteLine("Original string:")
        Console.WriteLine(unicodeString)

        ' Encode the string.
        Dim encodedBytes As Byte() = uni.GetBytes(unicodeString)
        Console.WriteLine()
        Console.WriteLine("Encoded bytes:")
        Dim b As Byte
        For Each b In  encodedBytes
            Console.Write("[{0}]", b)
        Next b
        Console.WriteLine()

        ' Decode bytes back to string.
        ' Notice Pi and Sigma characters are still present.
        Dim decodedString As String = uni.GetString(encodedBytes)
        Console.WriteLine()
        Console.WriteLine("Decoded bytes:")
        Console.WriteLine(decodedString)
    End Sub
End Class


.NET Framework

Supported in: 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

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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

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

Community Additions

ADD
Show:
© 2014 Microsoft