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

When overridden in a derived class, 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)


Public MustOverride Function GetCharCount ( _
    bytes As Byte(), _
    index As Integer, _
    count As Integer _
) As Integer
public abstract int GetCharCount(
    byte[] bytes,
    int index,
    int count


  • 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.

Return Value

Type: System.Int32
The number of characters produced by decoding the specified sequence of bytes and any bytes in the internal buffer.


Exception Condition

bytes is null (Nothing).


index or count is less than zero.


index and count do not denote a valid range in bytes.


A fallback occurred (see Understanding Encodings for fuller explanation).


This method does not affect the state of the decoder.

The GetCharCount(array<Byte[], Int32, Int32) method calculates the exact array size that the GetChars method requires to store the decoded characters.

If GetChars is called with flush set to false, the decoder stores trailing bytes at the end of the data block in an internal buffer and uses them in the next decoding operation. The application should call GetCharCount on a block of data immediately before calling GetChars on the same block, so that any trailing bytes from the previous block are included in the calculation.


The following code example demonstrates how to use the GetCharCount method to calculate the number of characters required to decode the specified range of bytes in the array.

Imports System.Text

Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim bytes() As Byte = { _
          85, 0, 110, 0, 105, 0, 99, 0, 111, 0, 100, 0, 101, 0 _

      Dim uniDecoder As Decoder = Encoding.Unicode.GetDecoder()
      Dim charCount As Integer = uniDecoder.GetCharCount(bytes, 0, bytes.Length)
      outputBlock.Text += String.Format("{0} characters needed to decode bytes.", charCount) & vbCrLf
   End Sub
End Class
using System;
using System.Text;

class Example
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
      Byte[] bytes = new Byte[] {
            85, 0, 110, 0, 105, 0, 99, 0, 111, 0, 100, 0, 101, 0

      Decoder uniDecoder = Encoding.Unicode.GetDecoder();
      int charCount = uniDecoder.GetCharCount(bytes, 0, bytes.Length);
      outputBlock.Text += String.Format(
          "{0} characters needed to decode bytes.", charCount
      ) + "\n";

Version Information


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


For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.