Encoding.GetCharCount Method (array<Byte[], Int32, Int32)
Microsoft Silverlight will reach end of support after October 2021. Learn more.
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)
Syntax
'Declaration
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
)
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. |
| 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 converts a string from one encoding to another.
Imports System.Text
Class Example
Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
Dim unicodeString As String = "This string contains the unicode character Pi(" & ChrW(&H3A0) & ")"
' Create two different encodings.
Dim utf8 As Encoding = Encoding.UTF8
Dim unicode As Encoding = Encoding.Unicode
' Convert the string into a byte[].
Dim unicodeBytes As Byte() = unicode.GetBytes(unicodeString)
' Perform the conversion from one encoding to the other.
Dim utf8Bytes As Byte() = Encoding.Convert(unicode, utf8, unicodeBytes)
' Convert the new byte[] into a char[] and then into a string.
Dim utf8Chars(utf8.GetCharCount(utf8Bytes, 0, utf8Bytes.Length) - 1) As Char
utf8.GetChars(utf8Bytes, 0, utf8Bytes.Length, utf8Chars, 0)
Dim utf8String As New String(utf8Chars)
' Display the strings created before and after the conversion.
outputBlock.Text += String.Format("Original string: {0}", unicodeString) & vbCrLf
outputBlock.Text += String.Format("Ascii converted string: {0}", utf8String) & vbCrLf
End Sub
End Class
' The example displays the following output:
' Original string: This string contains the unicode character Pi (Π)
' Ascii converted string: This string contains the unicode character Pi (?)
using System;
using System.Text;
class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
string unicodeString = "This string contains the unicode character Pi (\u03a0)";
// Create two different encodings.
Encoding utf8 = Encoding.UTF8;
Encoding unicode = Encoding.Unicode;
// Convert the string into a byte[].
byte[] unicodeBytes = unicode.GetBytes(unicodeString);
// Perform the conversion from one encoding to the other.
byte[] utf8Bytes = Encoding.Convert(unicode, utf8, unicodeBytes);
// Convert the new byte[] into a char[] and then into a string.
char[] utf8Chars = new char[utf8.GetCharCount(utf8Bytes, 0, utf8Bytes.Length)];
utf8.GetChars(utf8Bytes, 0, utf8Bytes.Length, utf8Chars, 0);
string utf8String = new string(utf8Chars);
// Display the strings created before and after the conversion.
outputBlock.Text += String.Format("Original string: {0}", unicodeString) + "\n";
outputBlock.Text += String.Format("Ascii converted string: {0}", utf8String) + "\n";
}
}
// The example displays the following output:
// Original string: This string contains the unicode character Pi (Π)
// Ascii converted string: This string contains the unicode character Pi (?)
The following code example encodes a string into an array of bytes, and then decodes a range of 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 barrBE 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 barrLE 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, decode eight bytes starting at index 0,
' and print out the counts and the resulting bytes.
outputBlock.Text &= "BE array with BE encoding : "
PrintCountsAndChars(outputBlock, barrBE, 0, 8, u32BE)
outputBlock.Text &= "LE array with LE encoding : "
PrintCountsAndChars(outputBlock, barrLE, 0, 8, u32LE)
End Sub 'Main
Public Shared Sub PrintCountsAndChars(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal bytes() As Byte, ByVal index As Integer, ByVal count As Integer, 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, index, count)
outputBlock.Text += String.Format(" {0,-3}", iCC)
' Display the maximum character count.
Dim iMCC As Integer = enc.GetMaxCharCount(count)
outputBlock.Text += String.Format(" {0,-3} :", iMCC)
' Decode the bytes.
Dim chars As Char() = enc.GetChars(bytes, index, count)
' The following is an alternative way to decode the bytes:
' 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 chars(iCC - 1) As Char
' enc.GetChars( bytes, index, count, chars, 0 )
' Display the characters.
outputBlock.Text &= chars & vbCrLf
End Sub 'PrintCountsAndChars
End Class 'SamplesEncoding
'This code produces the following output. The question marks take the place of characters that cannot be displayed at the console.
'
'BE array with BE encoding : System.Text.UTF32Encoding : 2 6 :za
'LE array with LE encoding : System.Text.UTF32Encoding : 2 6 :za
using System;
using System.Text;
public class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
// Create two instances of UTF32Encoding: one with little-endian byte order and one with big-endian byte order.
Encoding u32LE = Encoding.GetEncoding("utf-32");
Encoding u32BE = 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)
String myStr = "za\u0306\u01FD\u03B2";
// Encode the string using the big-endian byte order.
byte[] barrBE = new byte[u32BE.GetByteCount(myStr)];
u32BE.GetBytes(myStr, 0, myStr.Length, barrBE, 0);
// Encode the string using the little-endian byte order.
byte[] barrLE = new byte[u32LE.GetByteCount(myStr)];
u32LE.GetBytes(myStr, 0, myStr.Length, barrLE, 0);
// Get the char counts, decode eight bytes starting at index 0,
// and print out the counts and the resulting bytes.
outputBlock.Text += "BE array with BE encoding : ";
PrintCountsAndChars(outputBlock, barrBE, 0, 8, u32BE);
outputBlock.Text += "LE array with LE encoding : ";
PrintCountsAndChars(outputBlock, barrLE, 0, 8, u32LE);
}
public static void PrintCountsAndChars(System.Windows.Controls.TextBlock outputBlock, byte[] bytes, int index, int count, Encoding enc)
{
// Display the name of the encoding used.
outputBlock.Text += String.Format("{0,-25} :", enc.ToString());
// Display the exact character count.
int iCC = enc.GetCharCount(bytes, index, count);
outputBlock.Text += String.Format(" {0,-3}", iCC);
// Display the maximum character count.
int iMCC = enc.GetMaxCharCount(count);
outputBlock.Text += String.Format(" {0,-3} :", iMCC);
// Decode the bytes and display the characters.
char[] chars = enc.GetChars(bytes, index, count);
// The following is an alternative way to decode the bytes:
// char[] chars = new char[iCC];
// enc.GetChars( bytes, index, count, chars, 0 );
outputBlock.Text += chars + "\n";
}
}
/*
This code produces the following output. The question marks take the place of characters that cannot be displayed at the console.
BE array with BE encoding : System.Text.UTF32Encoding : 2 6 :za
LE array with LE encoding : System.Text.UTF32Encoding : 2 6 :za
*/
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