GetDecoder Method

UTF8Encoding.GetDecoder Method

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

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)

'Declaration
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 UTF8Encoding.GetChars method. However, a Decoder object 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 operations in which a single set of data spans multiple blocks.

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 demonstrates how to use the GetDecoder method to obtain a UTF-8 decoder. The decoder converts a sequence of bytes into a sequence of characters.


Imports System.Text

Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      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 _
      )

      outputBlock.Text += String.Format("{0} characters used to decode bytes.", charsDecodedCount) & vbCrLf

      outputBlock.Text &= "Decoded chars: "
      Dim c As Char
      For Each c In chars
         outputBlock.Text += String.Format("[{0}]", c)
      Next c
      outputBlock.Text &= vbCrLf
   End Sub 'Main
End Class 'UTF8EncodingExample


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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