UTF8Encoding 建構函式

來源:

UTF8Encoding.cs

來源:

UTF8Encoding.cs

來源:

UTF8Encoding.cs

public:
 UTF8Encoding();

public UTF8Encoding ();

Public Sub New ()

範例

下列範例會建立新的 UTF8Encoding 實例，並顯示其名稱。

using namespace System;
using namespace System::Text;
int main()
{
   UTF8Encoding^ utf8 = gcnew UTF8Encoding;
   String^ encodingName = utf8->EncodingName;
   Console::WriteLine( "Encoding name: {0}", encodingName );
}

using System;
using System.Text;

class UTF8EncodingExample {
    public static void Main() {
        UTF8Encoding utf8 = new UTF8Encoding();
        String encodingName = utf8.EncodingName;
        Console.WriteLine("Encoding name: " + encodingName);
    }
}

Imports System.Text

Class UTF8EncodingExample
    
    Public Shared Sub Main()
        Dim utf8 As New UTF8Encoding()
        Dim encodingName As String = utf8.EncodingName
        Console.WriteLine("Encoding name: " & encodingName)
    End Sub
End Class

備註

此建構函式會建立實例，該實例未提供 Unicode 位元組順序標記，而且在偵測到不正確編碼時不會擲回例外狀況。

另請參閱

• GetPreamble()

來源:

UTF8Encoding.cs

來源:

UTF8Encoding.cs

來源:

UTF8Encoding.cs

public:
 UTF8Encoding(bool encoderShouldEmitUTF8Identifier);

public UTF8Encoding (bool encoderShouldEmitUTF8Identifier);

new System.Text.UTF8Encoding : bool -> System.Text.UTF8Encoding

Public Sub New (encoderShouldEmitUTF8Identifier As Boolean)

參數

範例

下列範例會建立新的 UTF8Encoding 實例，並指定 方法應該發出 GetPreamble Unicode 位元組順序標記前置詞。 方法 GetPreamble 接著會傳回 Unicode 位元組順序標記前置詞。

using namespace System;
using namespace System::Text;
using namespace System::Collections;
void ShowArray( Array^ theArray )
{
   IEnumerator^ myEnum = theArray->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      Object^ o = safe_cast<Object^>(myEnum->Current);
      Console::Write( "[{0}]", o );
   }

   Console::WriteLine();
}

int main()
{
   UTF8Encoding^ utf8 = gcnew UTF8Encoding;
   UTF8Encoding^ utf8EmitBOM = gcnew UTF8Encoding( true );
   Console::WriteLine( "utf8 preamble:" );
   ShowArray( utf8->GetPreamble() );
   Console::WriteLine( "utf8EmitBOM:" );
   ShowArray( utf8EmitBOM->GetPreamble() );
}

using System;
using System.Text;

class UTF8EncodingExample {
    public static void Main() {
        UTF8Encoding utf8 = new UTF8Encoding();
        UTF8Encoding utf8EmitBOM = new UTF8Encoding(true);

        Console.WriteLine("utf8 preamble:");
        ShowArray(utf8.GetPreamble());

        Console.WriteLine("utf8EmitBOM:");
        ShowArray(utf8EmitBOM.GetPreamble());
    }

    public static void ShowArray(Array theArray) {
        foreach (Object o in theArray) {
            Console.Write("[{0}]", o);
        }
        Console.WriteLine();
    }
}

Imports System.Text

Class UTF8EncodingExample
    
    Public Shared Sub Main()
        Dim utf8 As New UTF8Encoding()
        Dim utf8EmitBOM As New UTF8Encoding(True)
        
        Console.WriteLine("utf8 preamble:")
        ShowArray(utf8.GetPreamble())
        
        Console.WriteLine("utf8EmitBOM:")
        ShowArray(utf8EmitBOM.GetPreamble())
    End Sub
    
    
    Public Shared Sub ShowArray(theArray As Array)
        Dim o As Object
        For Each o In  theArray
            Console.Write("[{0}]", o)
        Next o
        Console.WriteLine()
    End Sub
End Class

備註

此建構函式會建立實例，在偵測到不正確編碼時不會擲回例外狀況。

參數 encoderShouldEmitUTF8Identifier 會控制 方法的 GetPreamble 作業。 如果 true 為 ，此方法會傳回位元組陣列，其中包含 UTF-8 格式的 Unicode 位元組順序標記 (BOM) 。 如果 false 為 ，則會傳回長度為零的位元組陣列。 不過，將 設定 encoderShouldEmitUTF8Identifiertrue 為 不會讓 GetBytes 方法在位元組陣列開頭加上 BOM，也不會造成 GetByteCount 方法在位元組計數的 BOM 中包含位元組數目。

另請參閱

• GetPreamble()

來源:

UTF8Encoding.cs

來源:

UTF8Encoding.cs

來源:

UTF8Encoding.cs

public:
 UTF8Encoding(bool encoderShouldEmitUTF8Identifier, bool throwOnInvalidBytes);

public UTF8Encoding (bool encoderShouldEmitUTF8Identifier, bool throwOnInvalidBytes);

new System.Text.UTF8Encoding : bool * bool -> System.Text.UTF8Encoding

Public Sub New (encoderShouldEmitUTF8Identifier As Boolean, throwOnInvalidBytes As Boolean)

參數

範例

下列範例會建立新的 UTF8Encoding 實例，指定 GetPreamble 方法不應該發出 Unicode 位元組順序標記前置詞，而且偵測到不正確編碼時，應該擲回例外狀況。 此建構函式的行為會與預設 UTF8Encoding() 建構函式進行比較，當偵測到不正確編碼時，不會擲回例外狀況。 兩 UTF8Encoding 個實例會編碼字元陣列，其中包含兩個高 Surrogate (U+D801 和 U+D802) 資料列中，這是不正確字元序列;高 Surrogate 應一律接在低 Surrogate 後面。

using namespace System;
using namespace System::Text;

void ShowArray(Array^ theArray)
{
   for each (Byte b in theArray) {
      Console::Write( "{0:X2} ", b);
   }
   Console::WriteLine();
}

int main()
{
   UTF8Encoding^ utf8 = gcnew UTF8Encoding;
   UTF8Encoding^ utf8ThrowException = gcnew UTF8Encoding(false,true);
   
   // This array contains two high surrogates in a row (\uD801, \uD802).
   array<Char>^chars = {'a','b','c',L'\xD801',L'\xD802','d'};
   
   // The following method call will not throw an exception.
   array<Byte>^bytes = utf8->GetBytes( chars );
   ShowArray( bytes );
   Console::WriteLine();
   
   try {
      
      // The following method call will throw an exception.
      bytes = utf8ThrowException->GetBytes( chars );
   }
   catch (EncoderFallbackException^ e ) {
            Console::WriteLine("{0} exception\nMessage:\n{1}",
                               e->GetType()->Name, e->Message);
   }

}

using System;
using System.Text;

class Example
{
    public static void Main()
    {
        UTF8Encoding utf8 = new UTF8Encoding();
        UTF8Encoding utf8ThrowException = new UTF8Encoding(false, true);

        // Create an array with two high surrogates in a row (\uD801, \uD802).
        Char[] chars = new Char[] {'a', 'b', 'c', '\uD801', '\uD802', 'd'};

        // The following method call will not throw an exception.
        Byte[] bytes = utf8.GetBytes(chars);
        ShowArray(bytes);
        Console.WriteLine();

        try {
            // The following method call will throw an exception.
            bytes = utf8ThrowException.GetBytes(chars);
            ShowArray(bytes);
        }
        catch (EncoderFallbackException e) {
            Console.WriteLine("{0} exception\nMessage:\n{1}",
                              e.GetType().Name, e.Message);
        }
    }

    public static void ShowArray(Array theArray) {
        foreach (Object o in theArray)
            Console.Write("{0:X2} ", o);

        Console.WriteLine();
    }
}
// The example displays the following output:
//    61 62 63 EF BF BD EF BF BD 64
//
//    EncoderFallbackException exception
//    Message:
//    Unable to translate Unicode character \uD801 at index 3 to specified code page.

Imports System.Text

Class Example
    Public Shared Sub Main()
        Dim utf8 As New UTF8Encoding()
        Dim utf8ThrowException As New UTF8Encoding(False, True)
        
        ' Create an array with two high surrogates in a row (\uD801, \uD802).
        Dim chars() As Char = {"a"c, "b"c, "c"c, ChrW(&hD801), ChrW(&hD802), "d"c}
        
        ' The following method call will not throw an exception.
        Dim bytes As Byte() = utf8.GetBytes(chars)
        ShowArray(bytes)
        Console.WriteLine()
        
        Try
            ' The following method call will throw an exception.
            bytes = utf8ThrowException.GetBytes(chars)
            ShowArray(bytes)
        Catch e As EncoderFallbackException
            Console.WriteLine("{0} exception{2}Message:{2}{1}",
                              e.GetType().Name, e.Message, vbCrLf)
        End Try
    End Sub
    
    
    Public Shared Sub ShowArray(theArray As Array)
        For Each o In theArray
            Console.Write("{0:X2} ", o)
        Next
        Console.WriteLine()
    End Sub
End Class
' The example displays the following output:
'    61 62 63 EF BF BD EF BF BD 64
'
'    EncoderFallbackException exception
'    Message:
'    Unable to translate Unicode character \uD801 at index 3 to specified code page.

備註

參數 encoderShouldEmitUTF8Identifier 會控制 方法的 GetPreamble 作業。 如果 true 為 ，此方法會傳回位元組陣列，其中包含 UTF-8 格式的 Unicode 位元組順序標記 (BOM) 。 如果 false 為 ，則會傳回長度為零的位元組陣列。 不過，將 設定 encoderShouldEmitUTF8Identifiertrue 為 不會讓 GetBytes 方法在位元組陣列開頭加上 BOM，也不會造成 GetByteCount 方法在位元組計數的 BOM 中包含位元組數目。

如果 throwOnInvalidBytes 為 true ，則偵測無效位元組序列的方法會 System.ArgumentException 擲回例外狀況。 否則，方法不會擲回例外狀況，而且會忽略不正確序列。

另請參閱

• GetPreamble()