UTF8Encoding.GetDecoder Method ()


Obtains a decoder that converts a UTF-8 encoded sequence of bytes into a sequence of Unicode characters.

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

Public Overrides Function GetDecoder As Decoder

Return Value

Type: System.Text.Decoder

A decoder that converts a UTF-8 encoded sequence of bytes into a sequence of Unicode characters.

The Decoder.GetChars method converts sequential blocks of bytes into sequential blocks of characters, in a manner similar to the GetChars method of this class. However, a Decoder maintains state information between calls so it can correctly decode byte sequences that span blocks. The Decoder also preserves trailing bytes at the end of data blocks and uses the trailing bytes in the next decoding operation. Therefore, GetDecoder and GetEncoder are useful for network transmission and file operations, because those operations often deal with blocks of data instead of a complete data stream.

If error detection is enabled, that is, the throwOnInvalidCharacters parameter of the constructor is set to true, error detection is also enabled in the Decoder returned by this method. If error detection is enabled and an invalid sequence is encountered, the state of the decoder is undefined and processing must stop.

The following example uses the GetDecoder method to obtain a UTF-8 decoder. The decoder converts a sequence of bytes into a sequence of characters.

Imports System
Imports System.Text

Class UTF8EncodingExample

    Public Shared Sub Main()
        Dim chars() As Char
        Dim bytes() As Byte = {99, 204, 128, 234, 130, 160}

        Dim utf8Decoder As Decoder = Encoding.UTF8.GetDecoder()

        Dim charCount As Integer = utf8Decoder.GetCharCount(bytes, 0, bytes.Length)
        chars = New Char(charCount - 1) {}
        Dim charsDecodedCount As Integer = utf8Decoder.GetChars( _
            bytes, 0, bytes.Length, chars, 0 _

        Console.WriteLine("{0} characters used to decode bytes.", charsDecodedCount)

        Console.Write("Decoded chars: ")
        Dim c As Char
        For Each c In  chars
            Console.Write("[{0}]", c)
        Next c
    End Sub 'Main
End Class 'UTF8EncodingExample

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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