UTF8Encoding

Implements:

Public:

Properties:

Name	Description
BodyName (get)	Gets the encoding name to be used in with the mail agent body tags.
CodePage (get)	Gets the code page identifier for this encoding.
DecoderFallback (get)	Gets the DecoderFallback object for the current Encoding object.
DecoderFallback (set)	Sets the DecoderFallback object for the current Encoding object.
EncoderFallback (get)	Gets the EncoderFallback object for the current Encoding object.
EncoderFallback (set)	Sets the EncoderFallback object for the current Encoding object.
EncodingName (get)	Gets the human-readable description of the current encoding.
HeaderName (get)	Gets the encoding name to be used in with the mail agent header tags.
IsBrowserDisplay (get)	Gets if this encoding can be used by browsers to display text.
IsBrowserSave (get)	Gets if this encoding can be used to save data with this encoding.
IsMailNewsDisplay (get)	Gets if this encoding can be used to display mail and news by mail and news clients.
IsMailNewsSave (get)	Gets if this encoding can be used to save data by mail and news clients.
IsReadOnly (get)	When implemented in a derived class, gets a value indicating whether the current encoding is read-only.
IsSingleByte (get)	Gets if the current encoding uses single-byte code points.
WebName (get)	Gets the encoding name registered with the Internet Assigned Numbers Authority.
WindowsCodePage (get)	Gets the Windows Operating Systems code page for this encoding.

Methods:

Name	Description
Clone	Creates a clone of the current Encoding instance.
Equals	Determines whether the specified value is equal to the current UTF8Encoding object.
GetByteCount	Calculates the number of bytes produced by encoding the characters in the specified String or Integer().
GetBytes	Encodes all the characters in the specified character array or string into a sequence of bytes.
GetBytesEx	Encodes a set of characters into an array of bytes, returning the number of bytes produced.
GetCharCount	Calculates the number of characters produced by decoding a sequence of bytes from the specified byte array.
GetChars	Decodes a sequence of bytes from the specified byte array into a set of characters.
GetCharsEx	Decodes a sequence of bytes from the specified byte array into the specified character array.
GetDecoder	Obtains a decoder that converts a UTF-8 encoded sequence of bytes into a sequence of Unicode characters.
GetEncoder	Obtains an encoder that converts a sequence of Unicode characters into a UTF-8 encoded sequence of bytes.
GetHashCode	Returns the hash code for the current instance.
GetMaxByteCount	Calculates the maximum number of bytes produced by encoding the specified number of characters.
GetMaxCharCount	Calculates the maximum number of characters produced by decoding the specified number of bytes.
GetPreamble	Returns a Unicode byte order mark encoded in UTF-8 format, if the constructor for this instance requests a byte order mark.
GetString	Decodes a range of bytes from a byte array into a string.
ToString	Returns a string representation of the current object.

Remarks

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.

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

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.

UTF8Encoding corresponds to the Windows code page 65001.

Optionally, the UTF8Encoding 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. For more information on byte order and the byte order mark, see The Unicode Standard at the Unicode home page.

Examples

The following example demonstrates how to use a UTF8Encoding to encode a string of Unicode characters and store them in a byte array. Notice that when encodedBytes is decoded back to a string there is no loss of data.

Public Sub Main()
    Dim UTF8            As New UTF8Encoding
    Dim UnicodeString   As String
    Dim EncodedBytes()  As Byte
    Dim DecodedString   As String
    Dim b               As Variant
    
    Set Console.OutputEncoding = Encoding.UTF8
    
    ' A Unicode string with two characters outside an 8-bit code range.
    UnicodeString = t("This unicode string contains two characters with codes outside an 8-bit code range, Pi (\u03a0) and Sigma (\u03a3).")
    Console.WriteLine "Original string:"
    Console.WriteLine UnicodeString
    
    ' Encode the string.
    EncodedBytes = UTF8.GetBytes(UnicodeString)
    Console.WriteLine
    Console.WriteLine "Encoded bytes:"
    
    For Each b In EncodedBytes
        Console.WriteValue "[{0}]", b
    Next
    Console.WriteLine
    
    ' Decode bytes back to string.
    ' Notice Pi and Sigma characters are still present.
    DecodedString = UTF8.GetString(EncodedBytes)
    Console.WriteLine
    Console.WriteLine "Decoded bytes:"
    Console.WriteLine DecodedString
    Console.ReadKey
End Sub

See Also

Project CorLib Overview

Class UTF8Encoding Overview

Encoding

ASCIIEncoding

UTF7Encoding

UTF32Encoding

UnicodeEncoding