Articolo
11/18/2011

UTF8Encoding.GetChars Method (array<Byte[], Int32, Int32, array<Char[], Int32)

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

Decodes a sequence of bytes from the specified byte array into the specified character array.

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

Syntax

'Declaration
<SecuritySafeCriticalAttribute> _
Public Overrides Function GetChars ( _
    bytes As Byte(), _
    byteIndex As Integer, _
    byteCount As Integer, _
    chars As Char(), _
    charIndex As Integer _
) As Integer

[SecuritySafeCriticalAttribute]
public override 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	Error detection is enabled, and bytes contains an invalid sequence of bytes. -or- 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 complete explanation).

Remarks

To calculate the exact array size required by GetChars to store the resulting characters, call the GetCharCount method. To calculate the maximum array size, call the GetMaxCharCount method. The GetCharCount method generally allocates less memory, while the GetMaxCharCount method generally executes faster.

With error detection, an invalid sequence causes this method to throw a ArgumentException. Without error detection, invalid sequences are ignored, and no exception is thrown.

Data to be converted, such as data read from a stream, might be available only in sequential blocks. In this case, or if the amount of data is so large that it needs to be divided into smaller blocks, the application uses the Decoder or the Encoder provided by the GetDecoder method or the GetEncoder method, respectively.

Examples

The following example demonstrates how to use the GetChars method to decode a range of elements in a byte array and store the result in a 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, 84, 70, 56, 32, 69, 110, _
          99, 111, 100, 105, 110, 103, 32, _
          69, 120, 97, 109, 112, 108, 101 _
      }

      Dim utf8 As New UTF8Encoding()

      Dim charCount As Integer = utf8.GetCharCount(bytes, 2, 13)
      chars = New Char(charCount - 1) {}
      Dim charsDecodedCount As Integer = utf8.GetChars(bytes, 2, 13, 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[] {
             85,  84,  70,  56,  32,  69, 110,
             99, 111, 100, 105, 110, 103,  32,
             69, 120,  97, 109, 112, 108, 101
        };

      UTF8Encoding utf8 = new UTF8Encoding();

      int charCount = utf8.GetCharCount(bytes, 2, 13);
      chars = new Char[charCount];
      int charsDecodedCount = utf8.GetChars(bytes, 2, 13, 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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