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

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

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


<SecuritySafeCriticalAttribute> _
Public Overrides Function GetByteCount ( _
    chars As Char(), _
    index As Integer, _
    count As Integer _
) As Integer
public override int GetByteCount(
    char[] chars,
    int index,
    int count


  • 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.


Exception Condition

chars is null (Nothing).


index or count is less than zero.


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


The resulting number of bytes is greater than the maximum number that can be returned as an integer.


Error detection is enabled, and chars contains an invalid sequence of characters.


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


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.


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


The following code example demonstrates how to use the GetByteCount method to return the number of bytes required to encode an array of Unicode characters using UnicodeEncoding.

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 uni As New UnicodeEncoding()
      Dim byteCount As Integer = uni.GetByteCount(chars, 1, 2)
      outputBlock.Text += String.Format("{0} bytes needed to encode characters.", byteCount) & vbCrLf
   End Sub 'Main
End Class 'UnicodeEncodingExample
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

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