Encoding.GetByteCount Method (array<Char[], Int32, Int32)
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When overridden in a derived class, 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)
Syntax
'Declaration
Public MustOverride Function GetByteCount ( _
chars As Char(), _
index As Integer, _
count As Integer _
) As Integer
public abstract 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. |
| EncoderFallbackException | A fallback occurred (see Understanding Encodings for complete explanation). |
Remarks
To calculate the exact array size required by GetBytes to store the resulting bytes, the application should use GetByteCount. To calculate the maximum array size, the application should use GetMaxByteCount. The GetByteCount method generally allocates less memory, while the GetMaxByteCount 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 determines the number of bytes required to encode three characters from a character array, encodes the characters, and displays the resulting bytes.
Imports System.Text
Public Class Example
Private Shared outputBlock As System.Windows.Controls.TextBlock
Public Shared Sub Demo(ByVal outBlock As System.Windows.Controls.TextBlock)
outputBlock = outBlock
' The characters to encode:
' 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)
' a high-surrogate value (U+D8FF)
' a low-surrogate value (U+DCFF)
Dim myChars() As Char = {"z"c, "a"c, ChrW(&H306), ChrW(&H1FD), ChrW(&H3B2), ChrW(&HD8FF), ChrW(&HDCFF)}
' Get different encodings.
Dim u8 As Encoding = Encoding.UTF8
Dim u16LE As Encoding = Encoding.Unicode
Dim u16BE As Encoding = Encoding.BigEndianUnicode
' Encode three characters starting at index 4, and print out the counts and the resulting bytes.
PrintCountsAndBytes(myChars, 4, 3, u8)
PrintCountsAndBytes(myChars, 4, 3, u16LE)
PrintCountsAndBytes(myChars, 4, 3, u16BE)
End Sub
Public Shared Sub PrintCountsAndBytes(ByVal chars() As Char, ByVal index As Integer, _
ByVal count As Integer, ByVal enc As Encoding)
' Display the name of the encoding used.
outputBlock.Text += String.Format("{0,-30} :", enc.ToString())
' Display the exact byte count.
Dim iBC As Integer = enc.GetByteCount(chars, index, count)
outputBlock.Text += String.Format(" {0,-3}", iBC)
' Display the maximum byte count.
Dim iMBC As Integer = enc.GetMaxByteCount(count)
outputBlock.Text += String.Format(" {0,-3} :", iMBC)
' Encode the array of chars.
Dim bytes As Byte() = enc.GetBytes(chars, index, count)
' The following is an alternative way to encode the array of chars:
' The following line creates the array with the exact number of elements required.
' Dim bytes(iBC - 1) As Byte
' enc.GetBytes( chars, index, count, bytes, bytes.GetLowerBound(0) )
' Display all the encoded bytes.
PrintHexBytes(bytes)
End Sub
Public Shared Sub PrintHexBytes(ByVal bytes() As Byte)
If bytes Is Nothing OrElse bytes.Length = 0 Then
outputBlock.Text &= "<none>" & vbCrLf
Else
Dim i As Integer
For i = 0 To bytes.Length - 1
outputBlock.Text += String.Format("{0:X2} ", bytes(i))
Next i
outputBlock.Text &= vbCrLf
End If
End Sub
End Class
' This example produces the following output.
' System.Text.UTF8Encoding : 6 12 :CE B2 F1 8F B3 BF
' System.Text.UnicodeEncoding : 6 8 :B2 03 FF D8 FF DC
' System.Text.UnicodeEncoding : 6 8 :03 B2 D8 FF DC FF
using System;
using System.Text;
public class Example
{
private static System.Windows.Controls.TextBlock outputBlock;
public static void Demo(System.Windows.Controls.TextBlock outBlock)
{
outputBlock = outBlock;
// The characters to encode:
// 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)
// a high-surrogate value (U+D8FF)
// a low-surrogate value (U+DCFF)
char[] myChars = new char[] { 'z', 'a', '\u0306', '\u01FD', '\u03B2', '\uD8FF', '\uDCFF' };
// Get different encodings.
Encoding u8 = Encoding.UTF8;
Encoding u16LE = Encoding.Unicode;
Encoding u16BE = Encoding.BigEndianUnicode;
// Encode three characters starting at index 4, and print out the counts and the resulting bytes.
PrintCountsAndBytes(myChars, 4, 3, u8);
PrintCountsAndBytes(myChars, 4, 3, u16LE);
PrintCountsAndBytes(myChars, 4, 3, u16BE);
}
public static void PrintCountsAndBytes(char[] chars, int index, int count, Encoding enc)
{
// Display the name of the encoding used.
outputBlock.Text += String.Format("{0,-30} :", enc.ToString());
// Display the exact byte count.
int iBC = enc.GetByteCount(chars, index, count);
outputBlock.Text += String.Format(" {0,-3}", iBC);
// Display the maximum byte count.
int iMBC = enc.GetMaxByteCount(count);
outputBlock.Text += String.Format(" {0,-3} :", iMBC);
// Encode the array of chars.
byte[] bytes = enc.GetBytes(chars, index, count);
// The following is an alternative way to encode the array of chars:
// byte[] bytes = new byte[iBC];
// enc.GetBytes( chars, index, count, bytes, bytes.GetLowerBound(0) );
// Display all the encoded bytes.
PrintHexBytes(bytes);
}
public static void PrintHexBytes(byte[] bytes)
{
if ((bytes == null) || (bytes.Length == 0))
outputBlock.Text += "<none>" + "\n";
else
{
for (int i = 0; i < bytes.Length; i++)
outputBlock.Text += String.Format("{0:X2} ", bytes[i]);
outputBlock.Text += "\n";
}
}
}
/*
This example produces the following output.
System.Text.UTF8Encoding : 6 12 :CE B2 F1 8F B3 BF
System.Text.UnicodeEncoding : 6 8 :B2 03 FF D8 FF DC
System.Text.UnicodeEncoding : 6 8 :03 B2 D8 FF DC FF
*/
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.
See Also