Articolo
11/17/2011

UTF8Encoding.GetBytes Method (String, Int32, Int32, array<Byte[], Int32)

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

Encodes a set of characters from the specified string into the specified byte array.

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

Syntax

'Declaration
<SecuritySafeCriticalAttribute> _
Public Overrides Function GetBytes ( _
    s As String, _
    charIndex As Integer, _
    charCount As Integer, _
    bytes As Byte(), _
    byteIndex As Integer _
) As Integer

[SecuritySafeCriticalAttribute]
public override int GetBytes(
    string s,
    int charIndex,
    int charCount,
    byte[] bytes,
    int byteIndex
)

Parameters

s
Type: System.String
The string that contains the set of characters to encode.

charIndex
Type: System.Int32
The zero-based index of the first character to encode.

charCount
Type: System.Int32
The number of characters to encode.

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

byteIndex
Type: System.Int32
The zero-based index at which to start writing the resulting sequence of bytes.

Return Value

Type: System.Int32
The actual number of bytes written into bytes.

Exceptions

Exception	Condition
ArgumentNullException	s is nulla null reference (Nothing in Visual Basic). -or- bytes is nulla null reference (Nothing in Visual Basic).
ArgumentOutOfRangeException	charIndex or charCount or byteIndex is less than zero. -or- charIndex and charCount do not denote a valid range in chars. -or- byteIndex is not a valid index in bytes.
ArgumentException	Error detection is enabled, and s contains an invalid sequence of characters. -or- bytes does not have enough capacity from byteIndex to the end of the array to accommodate the resulting bytes.
EncoderFallbackException	A fallback occurred (see Understanding Encodings for complete explanation).

Remarks

To calculate the exact array size required by GetBytes to store the resulting bytes, call the GetByteCount method. To calculate the maximum array size, call the GetMaxByteCount method. The GetByteCount method generally allocates less memory, while the GetMaxByteCount 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.

Note:
To ensure that the encoded bytes are decoded properly, the application should prefix encoded bytes with a preamble.

Examples

The following example demonstrates how to use the GetBytes method to encode a range of elements from a Unicode character array, and store the encoded bytes in a range of elements in a byte array.

Imports System.Text
Imports Microsoft.VisualBasic.Strings

Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim bytes() As Byte
      ' Unicode characters.
      ' ChrW(35)  = #
      ' ChrW(37)  = %
      ' ChrW(928) = Pi
      ' ChrW(931) = Sigma
      Dim chars() As Char = {ChrW(35), ChrW(37), ChrW(928), ChrW(931)}

      Dim utf8 As New UTF8Encoding()

      Dim byteCount As Integer = utf8.GetByteCount(chars, 1, 2)
      bytes = New Byte(byteCount - 1) {}
      Dim bytesEncodedCount As Integer = utf8.GetBytes(chars, 1, 2, bytes, 0)

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

      outputBlock.Text &= "Encoded bytes: "
      Dim b As Byte
      For Each b In bytes
         outputBlock.Text += String.Format("[{0}]", b)
      Next b
      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)
   {
      Byte[] bytes;
      // Unicode characters.
      Char[] chars = new Char[] {
            '\u0023', // #
            '\u0025', // %
            '\u03a0', // Pi
            '\u03a3'  // Sigma
        };

      UTF8Encoding utf8 = new UTF8Encoding();

      int byteCount = utf8.GetByteCount(chars, 1, 2);
      bytes = new Byte[byteCount];
      int bytesEncodedCount = utf8.GetBytes(chars, 1, 2, bytes, 0);

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

      outputBlock.Text += "Encoded bytes: ";
      foreach (Byte b in bytes)
      {
         outputBlock.Text += String.Format("[{0}]", b);
      }
      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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