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Encoding.GetCharCount Method (Byte())

Silverlight

When overridden in a derived class, calculates the number of characters produced by decoding all the bytes in the specified byte array.

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

Syntax

'Declaration
Public Overridable Function GetCharCount ( _
	bytes As Byte() _
) As Integer

Parameters

bytes: Type: System.Byte()
The byte array containing the sequence 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 Nothing.
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, the application should use GetCharCount. To calculate the maximum array size, the application should use GetMaxCharCount. The GetCharCount method generally allocates less memory, while the GetMaxCharCount method generally executes faster.

For a discussion of programming considerations for use of this method, see the Encoding class description.

Examples

The following code example encodes a string into an array of bytes, and then decodes the bytes into an array of characters.


Imports System.Text

Public Class Example
   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      ' Create two instances of UTF32Encoding: one with little-endian byte order and one with big-endian byte order.
      Dim u32LE As Encoding = Encoding.GetEncoding("utf-32")
      Dim u32BE As Encoding = Encoding.GetEncoding("utf-32BE")

      ' Use a string containing the following characters:
      '    Latin Small Letter Z (U+007A)
      '    Latin Small Letter A (U+0061)
      '    Combining Breve (U+0306)
      '    Latin Small Letter AE With Acute (U+01FD)
      '    Greek Small Letter Beta (U+03B2)
      Dim myStr As String = "za" & ChrW(&H306) & ChrW(&H1FD) & ChrW(&H3B2)

      ' Encode the string using the big-endian byte order.
      ' NOTE: In VB.NET, arrays contain one extra element by default.
      '       The following line creates the array with the exact number of elements required.
      Dim barrBE(u32BE.GetByteCount(myStr) - 1) As Byte
      u32BE.GetBytes(myStr, 0, myStr.Length, barrBE, 0)

      ' Encode the string using the little-endian byte order.
      ' NOTE: In VB.NET, arrays contain one extra element by default.
      '       The following line creates the array with the exact number of elements required.
      Dim barrLE(u32LE.GetByteCount(myStr) - 1) As Byte
      u32LE.GetBytes(myStr, 0, myStr.Length, barrLE, 0)

      ' Get the char counts, and decode the byte arrays.
      outputBlock.Text &= "BE array with BE encoding : "
      PrintCountsAndChars(outputBlock, barrBE, u32BE)
      outputBlock.Text &= "LE array with LE encoding : "
      PrintCountsAndChars(outputBlock, barrLE, u32LE)
   End Sub

   Public Shared Sub PrintCountsAndChars(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal bytes() As Byte, ByVal enc As Encoding)
      ' Display the name of the encoding used.
      outputBlock.Text += String.Format("{0,-25} :", enc.ToString())

      ' Display the exact character count.
      Dim iCC As Integer = enc.GetCharCount(bytes)
      outputBlock.Text += String.Format(" {0,-3}", iCC)

      ' Display the maximum character count.
      Dim iMCC As Integer = enc.GetMaxCharCount(bytes.Length)
      outputBlock.Text += String.Format(" {0,-3} :", iMCC)

      ' Decode the bytes and display the characters.
      Dim chars As Char() = enc.GetChars(bytes)
      outputBlock.Text &= chars & vbCrLf

   End Sub 
End Class


'This code produces the following output.
'
'    BE array with BE encoding : System.Text.UTF32Encoding : 5   12  :zăǽβ
'    LE array with LE encoding : System.Text.UTF32Encoding : 5   12  :zăǽβ
'