Encoding.GetCharCount 方法

参考

定义

命名空间:: System.Text

程序集:: System.Text.Encoding.dll

程序集:: System.Runtime.dll

程序集:: mscorlib.dll

程序集:: netstandard.dll

重要

一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。

在派生类中重写时，计算对字节序列进行解码所产生的字符数。

重载

GetCharCount(Byte[])	在派生类中重写时，计算对指定字节数组中的所有字节进行解码所产生的字符数。
GetCharCount(ReadOnlySpan<Byte>)	在派生类中重写时，计算对提供的只读字节范围进行解码所产生的字符数。
GetCharCount(Byte*, Int32)	在派生类中重写时，计算对字节序列（从指定的字节指针开始）进行解码所产生的字符数。
GetCharCount(Byte[], Int32, Int32)	在派生类中重写时，计算对字节序列（从指定字节数组开始）进行解码所产生的字符数。

GetCharCount(Byte[])

Source:: Encoding.cs

Source:: Encoding.cs

Source:: Encoding.cs

在派生类中重写时，计算对指定字节数组中的所有字节进行解码所产生的字符数。

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

参数

bytes: Byte[]

包含要解码的字节序列的字节数组。

Int32

对指定字节序列进行解码所产生的字符数。

例外

ArgumentNullException

bytes 为 null。

DecoderFallbackException

发生回退（有关详细信息，请参阅采用 .NET 的字符编码）

－和－

将 DecoderFallback 设置为 DecoderExceptionFallback。

示例

下面的示例将字符串编码为一个字节数组，然后将这些字节解码为一个字符数组。

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

注解

若要计算存储所生成的字符所需的确切数组大小 GetChars(Byte[]) ，应使用 GetCharCount(Byte[]) 方法。若要计算最大数组大小，应使用 GetMaxCharCount(Int32) 方法。 GetCharCount(Byte[])方法通常允许分配较少的内存，而 GetMaxCharCount 方法的执行速度通常更快。

GetCharCount(Byte[])方法确定多少个字符会导致对一个字节序列进行解码，并且该 GetChars(Byte[]) 方法执行实际解码。 Encoding.GetChars方法需要分离转换，这与方法不同， Decoder.GetChars 后者处理单个输入流上的多个传递。

支持和的多个版本 GetCharCount GetChars 。下面是有关使用这些方法的一些编程注意事项：

您的应用程序可能需要从代码页解码多个输入字节，并使用多个调用处理这些字节。在这种情况下，可能需要在调用之间维护状态。
如果你的应用程序处理字符串输出，则应使用 GetString 方法。由于此方法必须检查字符串长度并分配一个缓冲区，因此它稍慢一些，但生成的 String 类型是首选的。
的字节版本 GetChars(Byte*, Int32, Char*, Int32) 允许一些快速的方法，尤其是对大缓冲区的多个调用。但请记住，此方法版本有时不安全，因为指针是必需的。
如果你的应用程序必须转换大量数据，则应重新使用输出缓冲区。在这种情况下， GetChars(Byte[], Int32, Int32, Char[], Int32) 支持输出字符缓冲区的版本是最佳选择。
请考虑使用 Decoder.Convert 方法而不是 GetCharCount 。转换方法尽可能多地转换数据，如果输出缓冲区太小，则会引发异常。对于流的连续解码，此方法通常是最佳选择。

另请参阅

适用于

GetCharCount(ReadOnlySpan<Byte>)

Source:: Encoding.cs

Source:: Encoding.cs

Source:: Encoding.cs

在派生类中重写时，计算对提供的只读字节范围进行解码所产生的字符数。

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

参数

bytes: ReadOnlySpan<Byte>

要解码的只读字节范围。

Int32

对字节范围进行解码所产生的字符数。

注解

若要计算 GetChars 存储所生成的字符所需的确切数组大小，应使用 GetCharCount 方法。若要计算最大数组大小，请使用 GetMaxCharCount 方法。 GetCharCount方法通常允许分配较少的内存，而 GetMaxCharCount 方法的执行速度通常更快。

GetCharCount方法确定多少个字符会导致对一个字节序列进行解码，并且该 GetChars 方法执行实际解码。 GetChars方法需要分离转换，这与方法不同， Decoder.GetChars 后者处理单个输入流上的多个传递。

支持和的多个版本 GetCharCount GetChars 。下面是有关使用这些方法的一些编程注意事项：

您的应用程序可能需要从代码页解码多个输入字节，并使用多个调用处理这些字节。在这种情况下，可能需要在调用之间维护状态。
如果你的应用程序处理字符串输出，则建议使用 GetString 方法。由于此方法必须检查字符串长度并分配一个缓冲区，因此它稍慢一些，但生成的 String 类型是首选的。
如果你的应用程序必须转换大量数据，则应重新使用输出缓冲区。在这种情况下， GetChars(Byte[], Int32, Int32, Char[], Int32) 支持输出字符缓冲区的版本是最佳选择。
请考虑使用 Decoder.Convert 方法而不是 GetCharCount 。转换方法尽可能多地转换数据，如果输出缓冲区太小，则会引发异常。对于流的连续解码，此方法通常是最佳选择。

适用于

GetCharCount(Byte*, Int32)

Source:: Encoding.cs

Source:: Encoding.cs

Source:: Encoding.cs

重要

此 API 不符合 CLS。

在派生类中重写时，计算对字节序列（从指定的字节指针开始）进行解码所产生的字符数。

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);

[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

[<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

参数

bytes: Byte*

指向第一个要解码的字节的指针。

count: Int32

要解码的字节数。

Int32

对指定字节序列进行解码所产生的字符数。

属性: CLSCompliantAttribute SecurityCriticalAttribute ComVisibleAttribute

例外

ArgumentNullException

bytes 为 null。

ArgumentOutOfRangeException

count 小于零。

DecoderFallbackException

发生回退（有关详细信息，请参阅采用 .NET 的字符编码）

－和－

将 DecoderFallback 设置为 DecoderExceptionFallback。

注解

支持和的多个版本 GetCharCount GetChars 。下面是有关使用这些方法的一些编程注意事项：

您的应用程序可能需要从代码页解码多个输入字节，并使用多个调用处理这些字节。在这种情况下，可能需要在调用之间维护状态。
如果你的应用程序处理字符串输出，则建议使用 GetString 方法。由于此方法必须检查字符串长度并分配一个缓冲区，因此它稍慢一些，但生成的 String 类型是首选的。
的字节版本 GetChars(Byte*, Int32, Char*, Int32) 允许一些快速的方法，尤其是对大缓冲区的多个调用。但请记住，此方法版本有时不安全，因为指针是必需的。
如果你的应用程序必须转换大量数据，则应重新使用输出缓冲区。在这种情况下， GetChars(Byte[], Int32, Int32, Char[], Int32) 支持输出字符缓冲区的版本是最佳选择。
请考虑使用 Decoder.Convert 方法而不是 GetCharCount 。转换方法尽可能多地转换数据，如果输出缓冲区太小，则会引发异常。对于流的连续解码，此方法通常是最佳选择。

另请参阅

适用于

GetCharCount(Byte[], Int32, Int32)

Source:: Encoding.cs

Source:: Encoding.cs

Source:: Encoding.cs

在派生类中重写时，计算对字节序列（从指定字节数组开始）进行解码所产生的字符数。

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

参数

bytes: Byte[]

包含要解码的字节序列的字节数组。

index: Int32

第一个要解码的字节的索引。

count: Int32

要解码的字节数。

Int32

对指定字节序列进行解码所产生的字符数。

例外

ArgumentNullException

bytes 为 null。

ArgumentOutOfRangeException

index 或 count 小于零。

或

index 和 count 不表示 bytes 中的有效范围。

DecoderFallbackException

发生回退（有关详细信息，请参阅采用 .NET 的字符编码）

－和－

将 DecoderFallback 设置为 DecoderExceptionFallback。

示例

下面的示例将字符串从一种编码转换为另一种编码。

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 (?)

下面的示例将字符串编码为一个字节数组，然后将一系列字节解码为字符数组。

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

注解

若要计算存储所生成的字符所需的确切数组大小 GetChars ，应使用 GetCharCount 方法。若要计算最大数组大小，请使用 GetMaxCharCount 方法。 GetCharCount方法通常允许分配较少的内存，而 GetMaxCharCount 方法的执行速度通常更快。

支持和的多个版本 GetCharCount GetChars 。下面是有关使用这些方法的一些编程注意事项：

您的应用程序可能需要从代码页解码多个输入字节，并使用多个调用处理这些字节。在这种情况下，可能需要在调用之间维护状态。
如果你的应用程序处理字符串输出，则建议使用 GetString 方法。由于此方法必须检查字符串长度并分配一个缓冲区，因此它稍慢一些，但生成的 String 类型是首选的。
的字节版本 GetChars(Byte*, Int32, Char*, Int32) 允许一些快速的方法，尤其是对大缓冲区的多个调用。但请记住，此方法版本有时不安全，因为指针是必需的。
如果你的应用程序必须转换大量数据，则应重新使用输出缓冲区。在这种情况下， GetChars(Byte[], Int32, Int32, Char[], Int32) 支持输出字符缓冲区的版本是最佳选择。
请考虑使用 Decoder.Convert 方法而不是 GetCharCount 。转换方法尽可能多地转换数据，如果输出缓冲区太小，则会引发异常。对于流的连续解码，此方法通常是最佳选择。

另请参阅

适用于

通过

Encoding.GetCharCount 方法

定义

重载

GetCharCount(Byte[])

参数

返回

例外

示例

注解

另请参阅

适用于

GetCharCount(ReadOnlySpan<Byte>)

参数

返回

注解

适用于

GetCharCount(Byte*, Int32)

参数

返回

例外

注解

另请参阅

适用于

GetCharCount(Byte[], Int32, Int32)

参数

返回

例外

示例

注解

另请参阅

适用于

其他资源