Artikel
11/17/2011

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

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

Calculates the number of bytes that would be produced by encoding a set of characters from the specified character array.

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

Syntax

'Declaration
<SecuritySafeCriticalAttribute> _
Public Overrides Function GetByteCount ( _
    chars As Char(), _
    index As Integer, _
    count As Integer _
) As Integer

[SecuritySafeCriticalAttribute]
public override int GetByteCount(
    char[] chars,
    int index,
    int count
)

Parameters

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

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

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

Return Value

Type: System.Int32
The number of bytes produced by encoding the specified characters.

Exceptions

Exception	Condition
ArgumentNullException	chars is nulla null reference (Nothing in Visual Basic).
ArgumentOutOfRangeException	index or count is less than zero. -or- index and count do not denote a valid range in chars. -or- The resulting number of bytes is greater than the maximum number that can be returned as an integer.
ArgumentException	Error detection is enabled, and chars contains an invalid sequence of characters.
EncoderFallbackException	A fallback occurred (see Understanding Encodings for complete explanation).

Remarks

To calculate the exact array size required by the GetBytes method 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.

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 GetByteCount method to return the number of bytes required to encode an array of Unicode characters, using UTF8Encoding.

Imports System.Text
Imports Microsoft.VisualBasic.Strings

Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      ' 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)
      outputBlock.Text += String.Format("{0} bytes needed to encode characters.", byteCount) & vbCrLf
   End Sub 'Main
End Class 'UTF8EncodingExample

using System;
using System.Text;

class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      // Unicode characters.
      Char[] chars = new Char[] {
            '\u0023', // #
            '\u0025', // %
            '\u03a0', // Pi
            '\u03a3'  // Sigma
        };

      UTF8Encoding utf8 = new UTF8Encoding();
      int byteCount = utf8.GetByteCount(chars, 1, 2);
      outputBlock.Text += String.Format(
          "{0} bytes needed to encode characters.", byteCount
      ) + "\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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