Article
11/18/2011

Decoder.GetChars Method (array<Byte[], Int32, Int32, array<Char[], Int32)

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When overridden in a derived class, decodes a sequence of bytes from the specified byte array and any bytes in the internal buffer into the specified character array.

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

Syntax

'Declaration
Public MustOverride Function GetChars ( _
    bytes As Byte(), _
    byteIndex As Integer, _
    byteCount As Integer, _
    chars As Char(), _
    charIndex As Integer _
) As Integer

public abstract int GetChars(
    byte[] bytes,
    int byteIndex,
    int byteCount,
    char[] chars,
    int charIndex
)

Parameters

bytes
Type: array<System.Byte[]
The byte array containing the sequence of bytes to decode.

byteIndex
Type: System.Int32
The zero-based index of the first byte to decode.

byteCount
Type: System.Int32
The number of bytes to decode.

chars
Type: array<System.Char[]
The character array to contain the resulting set of characters.

charIndex
Type: System.Int32
The zero-based index at which to start writing the resulting set of characters.

Return Value

Type: System.Int32
The actual number of characters written into chars.

Exceptions

Exception	Condition
ArgumentNullException	bytes is nulla null reference (Nothing in Visual Basic). -or- chars is nulla null reference (Nothing in Visual Basic).
ArgumentOutOfRangeException	byteIndex or byteCount or charIndex is less than zero. -or- byteindex and byteCount do not denote a valid range in bytes. -or- charIndex is not a valid index in chars.
ArgumentException	chars does not have enough capacity from charIndex to the end of the array to accommodate the resulting characters.
DecoderFallbackException	A fallback occurred (see Understanding Encodings for fuller explanation).

Remarks

The Decoder object saves state between calls to GetChars. When the application is done with a stream of data, it should set the flush parameter to true to make sure that the state information is flushed. With this setting, the decoder ignores invalid bytes at the end of the data block and clears the internal buffer.

To calculate the exact array size that GetChars requires to store the resulting characters, call the GetCharCount method.

If GetChars is called with flush set to false, the decoder stores trailing bytes at the end of the data block in an internal buffer and uses them in the next decoding operation. The application should call GetCharCount on a block of data immediately before calling GetChars on the same block, so that any trailing bytes from the previous block are included in the calculation.

Examples

The following example demonstrates how to decode a range of elements from a byte array and store them in a Unicode character array. The GetCharCount method is used to calculate the number of characters needed to store the decoded elements in the array bytes. The GetChars method decodes the specified elements in the byte array and stores them in the new character array.

Imports System.Text

Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim chars() As Char
      Dim bytes() As Byte = { _
          85, 0, 110, 0, 105, 0, 99, 0, 111, 0, 100, 0, 101, 0 _
      }

      Dim uniDecoder As Decoder = Encoding.Unicode.GetDecoder()

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

using System;
using System.Text;

class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      Char[] chars;
      Byte[] bytes = new Byte[] {
            85, 0, 110, 0, 105, 0, 99, 0, 111, 0, 100, 0, 101, 0
        };

      Decoder uniDecoder = Encoding.Unicode.GetDecoder();

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