Encoding.UTF8 屬性
定義
重要
部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。
會用 UTF-8 格式的編碼。
public:
static property System::Text::Encoding ^ UTF8 { System::Text::Encoding ^ get(); };public static System.Text.Encoding UTF8 { get; }static member UTF8 : System.Text.EncodingPublic Shared ReadOnly Property UTF8 As Encoding屬性值
UTF-8 格式的編碼。
範例
以下範例定義了一個由以下字元組成的陣列：
拉丁小寫字母Z（U+007A）
拉丁小寫字母 A（U+0061）
結合布雷夫（U+0306）
拉丁小寫 AE 帶尖音（U+01FD）
希臘小寫字母 BETA（U+03B2）
一對替代星（U+D800 U+DD54）形成希臘高音閣樓一千星（U+10154）。
它顯示每個字元的 UTF-16 碼單位，並決定 UTF-8 編碼器編碼字元陣列所需的位元組數。 接著編碼字元並顯示產生的 UTF-8 編碼位元組。
using System;
using System.Text;
public class Example
{
public static void Main()
{
// Create a character array.
string gkNumber = Char.ConvertFromUtf32(0x10154);
char[] chars = new char[] { 'z', 'a', '\u0306', '\u01FD', '\u03B2',
gkNumber[0], gkNumber[1] };
// Get UTF-8 and UTF-16 encoders.
Encoding utf8 = Encoding.UTF8;
Encoding utf16 = Encoding.Unicode;
// Display the original characters' code units.
Console.WriteLine("Original UTF-16 code units:");
byte[] utf16Bytes = utf16.GetBytes(chars);
foreach (var utf16Byte in utf16Bytes)
Console.Write("{0:X2} ", utf16Byte);
Console.WriteLine();
// Display the number of bytes required to encode the array.
int reqBytes = utf8.GetByteCount(chars);
Console.WriteLine("\nExact number of bytes required: {0}",
reqBytes);
// Display the maximum byte count.
int maxBytes = utf8.GetMaxByteCount(chars.Length);
Console.WriteLine("Maximum number of bytes required: {0}\n",
maxBytes);
// Encode the array of chars.
byte[] utf8Bytes = utf8.GetBytes(chars);
// Display all the UTF-8-encoded bytes.
Console.WriteLine("UTF-8-encoded code units:");
foreach (var utf8Byte in utf8Bytes)
Console.Write("{0:X2} ", utf8Byte);
Console.WriteLine();
}
}
// The example displays the following output:
// Original UTF-16 code units:
// 7A 00 61 00 06 03 FD 01 B2 03 00 D8 54 DD
//
// Exact number of bytes required: 12
// Maximum number of bytes required: 24
//
// UTF-8-encoded code units:
// 7A 61 CC 86 C7 BD CE B2 F0 90 85 94
Imports System.Text
Public Module Example
Public Sub Main()
' Create a character array.
Dim gkNumber As String = Char.ConvertFromUtf32(&h10154)
Dim chars() As Char = {"z"c, "a"c, ChrW(&H0306), ChrW(&H01FD),
ChrW(&H03B2), gkNumber(0), gkNumber(1) }
' Get UTF-8 and UTF-16 encoders.
Dim utf8 As Encoding = Encoding.UTF8
Dim utf16 As Encoding = Encoding.Unicode
' Display the original characters' code units.
Console.WriteLine("Original UTF-16 code units:")
Dim utf16Bytes() As Byte = utf16.GetBytes(chars)
For Each utf16Byte In utf16Bytes
Console.Write("{0:X2} ", utf16Byte)
Next
Console.WriteLine()
Console.WriteLine()
' Display the number of bytes required to encode the array.
Dim reqBytes As Integer = utf8.GetByteCount(chars)
Console.WriteLine("Exact number of bytes required: {0}",
reqBytes)
' Display the maximum byte count.
Dim maxBytes As Integer = utf8.GetMaxByteCount(chars.Length)
Console.WriteLine("Maximum number of bytes required: {0}",
maxBytes)
Console.WriteLine()
' Encode the array of characters.
Dim utf8Bytes() As Byte = utf8.GetBytes(chars)
' Display all the UTF-8-encoded bytes.
Console.WriteLine("UTF-8-encoded code units:")
For Each utf8Byte In utf8Bytes
Console.Write("{0:X2} ", utf8Byte)
Next
Console.WriteLine()
End Sub
End Module
' The example displays the following output:
' Original UTF-16 code units:
' 7A 00 61 00 06 03 FD 01 B2 03 00 D8 54 DD
'
' Exact number of bytes required: 12
' Maximum number of bytes required: 24
'
' UTF-8-encoded code units:
' 7A 61 CC 86 C7 BD CE B2 F0 90 85 94
備註
此特性回傳 UTF8Encoding 一個物件，將 Unicode（UTF-16 編碼）字元編碼為每個字元一到四個位元組的序列，並將 UTF-8 編碼的位元組陣列解碼為 Unicode（UTF-16 編碼）字元。 關於 .NET 支援的字元編碼及使用哪種 Unicode 編碼的討論，請參見 .NET<> 中的
UTF8Encoding這個屬性回傳的物件可能沒有適合你的應用程式的行為。
它會回傳一個 UTF8Encoding 物件，提供 Unicode 位元組順序標記（BOM）。 要實例化一個不提供 BOM 的 UTF8 編碼，請呼叫建構子的超載 UTF8Encoding 。
它會回傳一個 UTF8Encoding 物件，使用替換回備，將每個無法編碼的字串和每個無法解碼的位元組替換為問號（“？”）字元。 相反地，你可以呼叫建 UTF8Encoding.UTF8Encoding(Boolean, Boolean) 構子來實例化一個 UTF8Encoding 物件，其備用資源是 或 EncoderFallbackExceptionDecoderFallbackException，如下範例所示。
using System; using System.Text; public class Example { public static void Main() { Encoding enc = new UTF8Encoding(true, true); string value = "\u00C4 \uD802\u0033 \u00AE"; try { byte[] bytes= enc.GetBytes(value); foreach (var byt in bytes) Console.Write("{0:X2} ", byt); Console.WriteLine(); string value2 = enc.GetString(bytes); Console.WriteLine(value2); } catch (EncoderFallbackException e) { Console.WriteLine("Unable to encode {0} at index {1}", 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); } } } // The example displays the following output: // Unable to encode U+D802 at index 2Imports System.Text Module Example Public Sub Main() 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 Console.Write("{0:X2} ", byt) Next Console.WriteLine() Dim value2 As String = enc.GetString(bytes) Console.WriteLine(value2) Catch e As EncoderFallbackException Console.WriteLine("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) End Try End Sub End Module ' The example displays the following output: ' Unable to encode U+D802 at index 2