Encoding.GetByteCount Method (Char(), Int32, Int32)
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
When overridden in a derived class, calculates the number of bytes produced by encoding a set of characters from the specified character array.
Assembly: mscorlib (in mscorlib.dll)
'Declaration Public MustOverride Function GetByteCount ( _ chars As Char(), _ index As Integer, _ count As Integer _ ) As Integer
Parameters
- chars
- Type:
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.
| Exception | Condition |
|---|---|
| ArgumentNullException | chars is Nothing. |
| ArgumentOutOfRangeException | index or count is less than zero. -or- index and count do not denote a valid range in chars. |
| EncoderFallbackException | A fallback occurred. |
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.
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