Articolo
11/18/2011

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

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

Calculates the number of characters produced by decoding a sequence of bytes from the specified byte array.

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

Syntax

'Declaration
<SecuritySafeCriticalAttribute> _
Public Overrides Function GetCharCount ( _
    bytes As Byte(), _
    index As Integer, _
    count As Integer _
) As Integer

[SecuritySafeCriticalAttribute]
public override int GetCharCount(
    byte[] bytes,
    int index,
    int count
)

Parameters

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

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

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

Return Value

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

Exceptions

Exception	Condition
ArgumentNullException	bytes 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 bytes. -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 bytes contains an invalid sequence of bytes.
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.

Examples

The following example demonstrates how to use the GetCharCount method to return the number of characters produced by decoding a range of elements in a byte array.

Imports System.Text

Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      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, 8)
      outputBlock.Text += String.Format("{0} characters needed to decode bytes.", charCount) & 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 = 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, 8);
      outputBlock.Text += String.Format(
          "{0} characters needed to decode bytes.", charCount
      ) + "\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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