Article
11/18/2011

UTF8Encoding.GetDecoder Method

Microsoft Silverlight will reach end of support after October 2021. Learn more.

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)

Syntax

'Declaration
Public Overrides Function GetDecoder As Decoder

public override Decoder GetDecoder()

Return Value

Type: System.Text.Decoder
A Decoder that converts a UTF-8 encoded sequence of bytes into a sequence of Unicode characters.

Remarks

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.

Examples

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

using System;
using System.Text;

class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      Char[] chars;
      Byte[] bytes = new Byte[] {
            99, 204, 128, 234, 130, 160
        };

      Decoder utf8Decoder = Encoding.UTF8.GetDecoder();

      int charCount = utf8Decoder.GetCharCount(bytes, 0, bytes.Length);
      chars = new Char[charCount];
      int charsDecodedCount = utf8Decoder.GetChars(bytes, 0, bytes.Length, chars, 0);

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

      outputBlock.Text += "Decoded chars: ";
      foreach (Char c in chars)
      {
         outputBlock.Text += String.Format("[{0}]", c);
      }
      outputBlock.Text += "\n";
   }
}

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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