Encoding.GetCharCount 方法

參考

定義

命名空間:: System.Text

組件:: System.Text.Encoding.dll

組件:: System.Runtime.dll

組件:: netstandard.dll

組件:: mscorlib.dll

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。

在衍生類別中覆寫時，計算解碼位元組序列所產生的字元數目。

多載

GetCharCount(Byte[])	在衍生類別中覆寫時，計算解碼指定位元組陣列中所有位元組所產生的字元數目。
GetCharCount(ReadOnlySpan<Byte>)	在衍生類別中覆寫時，計算藉由解碼所提供唯讀位元組範圍時產生的字元數。
GetCharCount(Byte*, Int32)	在衍生類別中覆寫時，計算從指定的位元組指標開始，解碼位元組序列所產生的字元數目。
GetCharCount(Byte[], Int32, Int32)	在衍生類別中覆寫時，計算從指定的位元組陣列解碼位元組序列所產生的字元數目。

GetCharCount(Byte[])

在衍生類別中覆寫時，計算解碼指定位元組陣列中所有位元組所產生的字元數目。

public:
 virtual int GetCharCount(cli::array <System::Byte> ^ bytes);

public virtual int GetCharCount (byte[] bytes);

abstract member GetCharCount : byte[] -> int
override this.GetCharCount : byte[] -> int

Public Overridable Function GetCharCount (bytes As Byte()) As Integer

參數

bytes: Byte[]

包含要解碼之位元組序列的位元組陣列。

傳回

Int32

解碼指定位元組序列所產生的字元數。

例外狀況

ArgumentNullException

bytes 為 null。

DecoderFallbackException

發生後援 (如需詳細資訊，請參閱 .NET 中的字元編碼)

-和-

DecoderFallback 設定為 DecoderExceptionFallback。

範例

下列範例會將字串編碼為位元組陣列，然後將位元組解碼為字元陣列。

using namespace System;
using namespace System::Text;
void PrintCountsAndChars( array<Byte>^bytes, Encoding^ enc );
int main()
{
   
   // 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.
   array<Byte>^barrBE = gcnew array<Byte>(u32BE->GetByteCount( myStr ));
   u32BE->GetBytes( myStr, 0, myStr->Length, barrBE, 0 );
   
   // Encode the string using the little-endian byte order.
   array<Byte>^barrLE = gcnew array<Byte>(u32LE->GetByteCount( myStr ));
   u32LE->GetBytes( myStr, 0, myStr->Length, barrLE, 0 );
   
   // Get the char counts, and decode the byte arrays.
   Console::Write( "BE array with BE encoding : " );
   PrintCountsAndChars( barrBE, u32BE );
   Console::Write( "LE array with LE encoding : " );
   PrintCountsAndChars( barrLE, u32LE );
}

void PrintCountsAndChars( array<Byte>^bytes, Encoding^ enc )
{
   
   // Display the name of the encoding used.
   Console::Write( "{0,-25} :", enc );
   
   // Display the exact character count.
   int iCC = enc->GetCharCount( bytes );
   Console::Write( " {0,-3}", iCC );
   
   // Display the maximum character count.
   int iMCC = enc->GetMaxCharCount( bytes->Length );
   Console::Write( " {0,-3} :", iMCC );
   
   // Decode the bytes and display the characters.
   array<Char>^chars = enc->GetChars( bytes );
   Console::WriteLine( chars );
}

/* 
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 : 5   12  :zăǽβ
LE array with LE encoding : System.Text.UTF32Encoding : 5   12  :zăǽβ

*/

using System;
using System.Text;

public class SamplesEncoding  {

   public static void Main()  {

      // 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, and decode the byte arrays.
      Console.Write( "BE array with BE encoding : " );
      PrintCountsAndChars( barrBE, u32BE );
      Console.Write( "LE array with LE encoding : " );
      PrintCountsAndChars( barrLE, u32LE );
   }

   public static void PrintCountsAndChars( byte[] bytes, Encoding enc )  {

      // Display the name of the encoding used.
      Console.Write( "{0,-25} :", enc.ToString() );

      // Display the exact character count.
      int iCC  = enc.GetCharCount( bytes );
      Console.Write( " {0,-3}", iCC );

      // Display the maximum character count.
      int iMCC = enc.GetMaxCharCount( bytes.Length );
      Console.Write( " {0,-3} :", iMCC );

      // Decode the bytes and display the characters.
      char[] chars = enc.GetChars( bytes );
      Console.WriteLine( chars );
   }
}


/* 
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 : 5   12  :zăǽβ
LE array with LE encoding : System.Text.UTF32Encoding : 5   12  :zăǽβ

*/

Imports System.Text

Public Class SamplesEncoding   

   Public Shared Sub Main()

      ' 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(&H0306) & ChrW(&H01FD) & ChrW(&H03B2) 

      ' Encode the string using the big-endian byte order.
      ' 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 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 the array 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, and decode the byte arrays.
      Console.Write("BE array with BE encoding : ")
      PrintCountsAndChars(barrBE, u32BE)
      Console.Write("LE array with LE encoding : ")
      PrintCountsAndChars(barrLE, u32LE)

   End Sub


   Public Shared Sub PrintCountsAndChars(bytes() As Byte, enc As Encoding)

      ' Display the name of the encoding used.
      Console.Write("{0,-25} :", enc.ToString())

      ' Display the exact character count.
      Dim iCC As Integer = enc.GetCharCount(bytes)
      Console.Write(" {0,-3}", iCC)

      ' Display the maximum character count.
      Dim iMCC As Integer = enc.GetMaxCharCount(bytes.Length)
      Console.Write(" {0,-3} :", iMCC)

      ' Decode the bytes and display the characters.
      Dim chars As Char() = enc.GetChars(bytes)
      Console.WriteLine(chars)

   End Sub

End Class


'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 : 5   12  :zăǽβ
'LE array with LE encoding : System.Text.UTF32Encoding : 5   12  :zăǽβ

備註

若要計算儲存產生的字元所需的確切陣列大小 GetChars(Byte[]) ，您應該使用 GetCharCount(Byte[]) 方法。若要計算最大陣列大小，您應該使用 GetMaxCharCount(Int32) 方法。 GetCharCount(Byte[])方法通常允許配置較少的記憶體，而 GetMaxCharCount 方法的執行速度通常更快。

GetCharCount(Byte[])方法會判斷產生一連串位元組的字元數，而且 GetChars(Byte[]) 方法會執行實際的解碼。 Encoding.GetChars方法預期會有離散的轉換，相較于在 Decoder.GetChars 單一輸入資料流程上處理多個傳遞的方法。

支援數種版本的 GetCharCount 和 GetChars 。以下是使用這些方法的一些程式設計考慮：

您的應用程式可能需要從字碼頁解碼多個輸入位元組，並使用多個呼叫來處理這些位元組。在此情況下，您可能需要維護呼叫之間的狀態。
如果您的應用程式會處理字串輸出，您應該使用 GetString 方法。由於這個方法必須檢查字串長度並配置緩衝區，因此稍微慢一點，但結果型別會是 String 慣用的。
的位元組版本 GetChars(Byte*, Int32, Char*, Int32) 允許一些快速的技術，特別是對大型緩衝區的多次呼叫。不過請記住，這個方法的版本有時是不安全的，因為指標是必要的。
如果您的應用程式必須轉換大量資料，則應該重複使用輸出緩衝區。在此情況下， GetChars(Byte[], Int32, Int32, Char[], Int32) 支援輸出字元緩衝區的版本是最佳選擇。
請考慮使用 Decoder.Convert 方法，而不是 GetCharCount 。轉換方法會盡可能轉換最多的資料，而且如果輸出緩衝區太小，則會擲回例外狀況。針對資料流程的連續解碼，這個方法通常是最好的選擇。

另請參閱

適用於

GetCharCount(ReadOnlySpan<Byte>)

在衍生類別中覆寫時，計算藉由解碼所提供唯讀位元組範圍時產生的字元數。

public:
 virtual int GetCharCount(ReadOnlySpan<System::Byte> bytes);

public virtual int GetCharCount (ReadOnlySpan<byte> bytes);

abstract member GetCharCount : ReadOnlySpan<byte> -> int
override this.GetCharCount : ReadOnlySpan<byte> -> int

Public Overridable Function GetCharCount (bytes As ReadOnlySpan(Of Byte)) As Integer

參數

bytes: ReadOnlySpan<Byte>

要解碼的唯讀位元組範圍。

傳回

Int32

解碼位元組範圍所產生的字元數。

備註

若要計算 GetChars 儲存產生的字元所需的確切陣列大小，您應該使用 GetCharCount 方法。若要計算陣列大小上限，請使用 GetMaxCharCount 方法。 GetCharCount方法通常允許配置較少的記憶體，而 GetMaxCharCount 方法的執行速度通常更快。

GetCharCount方法會判斷產生一連串位元組的字元數，而且 GetChars 方法會執行實際的解碼。 GetChars方法預期會有離散的轉換，相較于在 Decoder.GetChars 單一輸入資料流程上處理多個傳遞的方法。

支援數種版本的 GetCharCount 和 GetChars 。以下是使用這些方法的一些程式設計考慮：

您的應用程式可能需要從字碼頁解碼多個輸入位元組，並使用多個呼叫來處理這些位元組。在此情況下，您可能需要維護呼叫之間的狀態。
如果您的應用程式會處理字串輸出，建議使用 GetString 方法。由於這個方法必須檢查字串長度並配置緩衝區，因此稍微慢一點，但結果型別會是 String 慣用的。
如果您的應用程式必須轉換大量資料，則應該重複使用輸出緩衝區。在此情況下， GetChars(Byte[], Int32, Int32, Char[], Int32) 支援輸出字元緩衝區的版本是最佳選擇。
請考慮使用 Decoder.Convert 方法，而不是 GetCharCount 。轉換方法會盡可能轉換最多的資料，而且如果輸出緩衝區太小，則會擲回例外狀況。針對資料流程的連續解碼，這個方法通常是最好的選擇。

適用於

GetCharCount(Byte*, Int32)

重要

此 API 不符合 CLS 規範。

在衍生類別中覆寫時，計算從指定的位元組指標開始，解碼位元組序列所產生的字元數目。

public:
 virtual int GetCharCount(System::Byte* bytes, int count);

[System.CLSCompliant(false)]
[System.Security.SecurityCritical]
public virtual int GetCharCount (byte* bytes, int count);

[System.CLSCompliant(false)]
public virtual int GetCharCount (byte* bytes, int count);

public virtual int GetCharCount (byte* bytes, int count);

[System.CLSCompliant(false)]
[System.Runtime.InteropServices.ComVisible(false)]
public virtual int GetCharCount (byte* bytes, int count);

[System.CLSCompliant(false)]
[System.Security.SecurityCritical]
[System.Runtime.InteropServices.ComVisible(false)]
public virtual int GetCharCount (byte* bytes, int count);

[<System.CLSCompliant(false)>]
[<System.Security.SecurityCritical>]
abstract member GetCharCount : nativeptr<byte> * int -> int
override this.GetCharCount : nativeptr<byte> * int -> int

[<System.CLSCompliant(false)>]
abstract member GetCharCount : nativeptr<byte> * int -> int
override this.GetCharCount : nativeptr<byte> * int -> int

abstract member GetCharCount : nativeptr<byte> * int -> int
override this.GetCharCount : nativeptr<byte> * int -> int

[<System.CLSCompliant(false)>]
[<System.Runtime.InteropServices.ComVisible(false)>]
abstract member GetCharCount : nativeptr<byte> * int -> int
override this.GetCharCount : nativeptr<byte> * int -> int

[<System.CLSCompliant(false)>]
[<System.Security.SecurityCritical>]
[<System.Runtime.InteropServices.ComVisible(false)>]
abstract member GetCharCount : nativeptr<byte> * int -> int
override this.GetCharCount : nativeptr<byte> * int -> int

參數

bytes: Byte*

要解碼的第一個位元組指標。

count: Int32

要解碼的位元組數。

傳回

Int32

解碼指定位元組序列所產生的字元數。

屬性: CLSCompliantAttribute SecurityCriticalAttribute ComVisibleAttribute

例外狀況

ArgumentNullException

bytes 為 null。

ArgumentOutOfRangeException

count 小於零。

DecoderFallbackException

發生後援 (如需詳細資訊，請參閱 .NET 中的字元編碼)

-和-

DecoderFallback 設定為 DecoderExceptionFallback。

備註

支援數種版本的 GetCharCount 和 GetChars 。以下是使用這些方法的一些程式設計考慮：

您的應用程式可能需要從字碼頁解碼多個輸入位元組，並使用多個呼叫來處理這些位元組。在此情況下，您可能需要維護呼叫之間的狀態。
如果您的應用程式會處理字串輸出，建議使用 GetString 方法。由於這個方法必須檢查字串長度並配置緩衝區，因此稍微慢一點，但結果型別會是 String 慣用的。
的位元組版本 GetChars(Byte*, Int32, Char*, Int32) 允許一些快速的技術，特別是對大型緩衝區的多次呼叫。不過請記住，這個方法的版本有時是不安全的，因為指標是必要的。
如果您的應用程式必須轉換大量資料，則應該重複使用輸出緩衝區。在此情況下， GetChars(Byte[], Int32, Int32, Char[], Int32) 支援輸出字元緩衝區的版本是最佳選擇。
請考慮使用 Decoder.Convert 方法，而不是 GetCharCount 。轉換方法會盡可能轉換最多的資料，而且如果輸出緩衝區太小，則會擲回例外狀況。針對資料流程的連續解碼，這個方法通常是最好的選擇。

另請參閱

適用於

GetCharCount(Byte[], Int32, Int32)

在衍生類別中覆寫時，計算從指定的位元組陣列解碼位元組序列所產生的字元數目。

public:
 abstract int GetCharCount(cli::array <System::Byte> ^ bytes, int index, int count);

public abstract int GetCharCount (byte[] bytes, int index, int count);

abstract member GetCharCount : byte[] * int * int -> int

Public MustOverride Function GetCharCount (bytes As Byte(), index As Integer, count As Integer) As Integer

參數

bytes: Byte[]

包含要解碼之位元組序列的位元組陣列。

index: Int32

要解碼的第一個位元組索引。

count: Int32

要解碼的位元組數。

傳回

Int32

解碼指定位元組序列所產生的字元數。

例外狀況

ArgumentNullException

bytes 為 null。

ArgumentOutOfRangeException

index 或 count 小於零。

-或-

index 與 count 不代表 bytes 中有效的範圍。

DecoderFallbackException

發生後援 (如需詳細資訊，請參閱 .NET 中的字元編碼)

-和-

DecoderFallback 設定為 DecoderExceptionFallback。

範例

下列範例會將字串從一種編碼轉換成另一種編碼方式。

using namespace System;
using namespace System::Text;

int main()
{
   String^ unicodeString = "This string contains the unicode character Pi (\u03a0)";
   
   // Create two different encodings.
   Encoding^ ascii = Encoding::ASCII;
   Encoding^ unicode = Encoding::Unicode;
   
   // Convert the string into a byte array.
   array<Byte>^unicodeBytes = unicode->GetBytes( unicodeString );
   
   // Perform the conversion from one encoding to the other.
   array<Byte>^asciiBytes = Encoding::Convert( unicode, ascii, unicodeBytes );
   
   // Convert the new Byte into[] a char and[] then into a string.
   array<Char>^asciiChars = gcnew array<Char>(ascii->GetCharCount( asciiBytes, 0, asciiBytes->Length ));
   ascii->GetChars( asciiBytes, 0, asciiBytes->Length, asciiChars, 0 );
   String^ asciiString = gcnew String( asciiChars );
   
   // Display the strings created before and after the conversion.
   Console::WriteLine( "Original String*: {0}", unicodeString );
   Console::WriteLine( "Ascii converted String*: {0}", asciiString );
}
// 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
{
   static void Main()
   {
      string unicodeString = "This string contains the unicode character Pi (\u03a0)";

      // Create two different encodings.
      Encoding ascii = Encoding.ASCII;
      Encoding unicode = Encoding.Unicode;

      // Convert the string into a byte array.
      byte[] unicodeBytes = unicode.GetBytes(unicodeString);

      // Perform the conversion from one encoding to the other.
      byte[] asciiBytes = Encoding.Convert(unicode, ascii, unicodeBytes);
         
      // Convert the new byte[] into a char[] and then into a string.
      char[] asciiChars = new char[ascii.GetCharCount(asciiBytes, 0, asciiBytes.Length)];
      ascii.GetChars(asciiBytes, 0, asciiBytes.Length, asciiChars, 0);
      string asciiString = new string(asciiChars);

      // Display the strings created before and after the conversion.
      Console.WriteLine("Original string: {0}", unicodeString);
      Console.WriteLine("Ascii converted string: {0}", asciiString);
   }
}
// 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 (?)

Imports System.Text

Class Example
   Shared Sub Main()
      Dim unicodeString As String = "This string contains the unicode character Pi (" & ChrW(&H03A0) & ")"

      ' Create two different encodings.
      Dim ascii As Encoding = Encoding.ASCII
      Dim unicode As Encoding = Encoding.Unicode

      ' Convert the string into a byte array.
      Dim unicodeBytes As Byte() = unicode.GetBytes(unicodeString)

      ' Perform the conversion from one encoding to the other.
      Dim asciiBytes As Byte() = Encoding.Convert(unicode, ascii, unicodeBytes)

      ' Convert the new byte array into a char array and then into a string.
      Dim asciiChars(ascii.GetCharCount(asciiBytes, 0, asciiBytes.Length)-1) As Char
      ascii.GetChars(asciiBytes, 0, asciiBytes.Length, asciiChars, 0)
      Dim asciiString As New String(asciiChars)

      ' Display the strings created before and after the conversion.
      Console.WriteLine("Original string: {0}", unicodeString)
      Console.WriteLine("Ascii converted string: {0}", asciiString)
   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 (?)

下列範例會將字串編碼為位元組陣列，然後將位元組範圍解碼為字元陣列。

using namespace System;
using namespace System::Text;
void PrintCountsAndChars( array<Byte>^bytes, int index, int count, Encoding^ enc );
int main()
{
   
   // 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.
   array<Byte>^barrBE = gcnew array<Byte>(u32BE->GetByteCount( myStr ));
   u32BE->GetBytes( myStr, 0, myStr->Length, barrBE, 0 );
   
   // Encode the string using the little-endian byte order.
   array<Byte>^barrLE = gcnew array<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.
   Console::Write( "BE array with BE encoding : " );
   PrintCountsAndChars( barrBE, 0, 8, u32BE );
   Console::Write( "LE array with LE encoding : " );
   PrintCountsAndChars( barrLE, 0, 8, u32LE );
}

void PrintCountsAndChars( array<Byte>^bytes, int index, int count, Encoding^ enc )
{
   
   // Display the name of the encoding used.
   Console::Write( "{0,-25} :", enc );
   
   // Display the exact character count.
   int iCC = enc->GetCharCount( bytes, index, count );
   Console::Write( " {0,-3}", iCC );
   
   // Display the maximum character count.
   int iMCC = enc->GetMaxCharCount( count );
   Console::Write( " {0,-3} :", iMCC );
   
   // Decode the bytes and display the characters.
   array<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 );
   Console::WriteLine( chars );
}

/* 
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 SamplesEncoding  {

   public static void Main()  {

      // 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.
      Console.Write( "BE array with BE encoding : " );
      PrintCountsAndChars( barrBE, 0, 8, u32BE );
      Console.Write( "LE array with LE encoding : " );
      PrintCountsAndChars( barrLE, 0, 8, u32LE );
   }

   public static void PrintCountsAndChars( byte[] bytes, int index, int count, Encoding enc )  {

      // Display the name of the encoding used.
      Console.Write( "{0,-25} :", enc.ToString() );

      // Display the exact character count.
      int iCC  = enc.GetCharCount( bytes, index, count );
      Console.Write( " {0,-3}", iCC );

      // Display the maximum character count.
      int iMCC = enc.GetMaxCharCount( count );
      Console.Write( " {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 );

      Console.WriteLine( chars );
   }
}


/* 
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

*/

Imports System.Text

Public Class SamplesEncoding   

   Public Shared Sub Main()

      ' 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(&H0306) & ChrW(&H01FD) & ChrW(&H03B2)

      ' 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.
      Console.Write("BE array with BE encoding : ")
      PrintCountsAndChars(barrBE, 0, 8, u32BE)
      Console.Write("LE array with LE encoding : ")
      PrintCountsAndChars(barrLE, 0, 8, u32LE)

   End Sub


   Public Shared Sub PrintCountsAndChars(bytes() As Byte, index As Integer, count As Integer, enc As Encoding)

      ' Display the name of the encoding used.
      Console.Write("{0,-25} :", enc.ToString())

      ' Display the exact character count.
      Dim iCC As Integer = enc.GetCharCount(bytes, index, count)
      Console.Write(" {0,-3}", iCC)

      ' Display the maximum character count.
      Dim iMCC As Integer = enc.GetMaxCharCount(count)
      Console.Write(" {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.
      Console.WriteLine(chars)

   End Sub

End Class


'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

備註

若要計算儲存產生的字元所需的確切陣列大小 GetChars ，您應該使用 GetCharCount 方法。若要計算陣列大小上限，請使用 GetMaxCharCount 方法。 GetCharCount方法通常允許配置較少的記憶體，而 GetMaxCharCount 方法的執行速度通常更快。

支援數種版本的 GetCharCount 和 GetChars 。以下是使用這些方法的一些程式設計考慮：

您的應用程式可能需要從字碼頁解碼多個輸入位元組，並使用多個呼叫來處理這些位元組。在此情況下，您可能需要維護呼叫之間的狀態。
如果您的應用程式會處理字串輸出，建議使用 GetString 方法。由於這個方法必須檢查字串長度並配置緩衝區，因此稍微慢一點，但結果型別會是 String 慣用的。
的位元組版本 GetChars(Byte*, Int32, Char*, Int32) 允許一些快速的技術，特別是對大型緩衝區的多次呼叫。不過請記住，這個方法的版本有時是不安全的，因為指標是必要的。
如果您的應用程式必須轉換大量資料，則應該重複使用輸出緩衝區。在此情況下， GetChars(Byte[], Int32, Int32, Char[], Int32) 支援輸出字元緩衝區的版本是最佳選擇。
請考慮使用 Decoder.Convert 方法，而不是 GetCharCount 。轉換方法會盡可能轉換最多的資料，而且如果輸出緩衝區太小，則會擲回例外狀況。針對資料流程的連續解碼，這個方法通常是最好的選擇。

另請參閱

適用於

Encoding.GetCharCount 方法

定義

多載

GetCharCount(Byte[])

參數

傳回

例外狀況

範例

備註

另請參閱

適用於

GetCharCount(ReadOnlySpan<Byte>)

參數

傳回

備註

適用於

GetCharCount(Byte*, Int32)

參數

傳回

例外狀況

備註

另請參閱

適用於

GetCharCount(Byte[], Int32, Int32)

參數

傳回

例外狀況

範例

備註

另請參閱

適用於

其他資源