Encoding.UTF8 Property
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Gets an encoding for the UTF-8 format.
Assembly: mscorlib (in mscorlib.dll)
This property returns a UTF8Encoding object that encodes Unicode characters into a sequence of one to four bytes per character, and that decodes a UTF-8-encoded byte array to Unicode characters.
The UTF8Encoding object that is returned by this property may not have the appropriate behavior for your application. It uses replacement fallback to replace each string that it cannot encode and each byte that it cannot decode with a question mark ("?") character. Instead, you can call the UTF8Encoding.UTF8Encoding(Boolean, Boolean) constructor to instantiate a UTF8Encoding object whose fallback is either an EncoderFallbackException or a DecoderFallbackException, as the following example illustrates.
Imports System.Text Module Example Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock) Dim enc As Encoding = New UTF8Encoding(True, True) Dim value As String = String.Format("{0} {1}{2} {3}", ChrW(&h00C4), ChrW(&hD802), ChrW(&h0033), ChrW(&h00AE)) Try Dim bytes() As Byte = enc.GetBytes(value) For Each byt As Byte In bytes outputBlock.Text &= String.Format("{0:X2} ", byt) Next outputBlock.Text &= vbCrLf Dim value2 As String = enc.GetString(bytes, 0, bytes.Length) outputBlock.Text &= value2 & vbCrLf Catch e As EncoderFallbackException outputBlock.Text += String.Format("Unable to encode {0} at index {1}", If(e.IsUnknownSurrogate(), String.Format("U+{0:X4} U+{1:X4}", Convert.ToUInt16(e.CharUnknownHigh), Convert.ToUInt16(e.CharUnknownLow)), String.Format("U+{0:X4}", Convert.ToUInt16(e.CharUnknown))), e.Index) & vbCrLf End Try End Sub End Module ' The example displays the following output: ' Unable to encode U+D802 at index 2
The following code example determines the number of bytes required to encode 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 the entire array, and print out the counts and the resulting bytes. PrintCountsAndBytes(myChars, u8) PrintCountsAndBytes(myChars, u16LE) PrintCountsAndBytes(myChars, u16BE) End Sub Public Shared Sub PrintCountsAndBytes(ByVal chars() As Char, 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) outputBlock.Text += String.Format(" {0,-3}", iBC) ' Display the maximum byte count. Dim iMBC As Integer = enc.GetMaxByteCount(chars.Length) outputBlock.Text += String.Format(" {0,-3} :", iMBC) ' Encode the array of chars. Dim bytes As Byte() = enc.GetBytes(chars) ' 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 : 12 24 :7A 61 CC 86 C7 BD CE B2 F1 8F B3 BF ' System.Text.UnicodeEncoding : 14 16 :7A 00 61 00 06 03 FD 01 B2 03 FF D8 FF DC ' System.Text.UnicodeEncoding : 14 16 :00 7A 00 61 03 06 01 FD 03 B2 D8 FF DC FF