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UTF32Encoding.GetString(Byte[], Int32, Int32) 方法

定義

將位元組陣列中的某一段位元組範圍解碼成字串。

public:
 override System::String ^ GetString(cli::array <System::Byte> ^ bytes, int index, int count);
public override string GetString (byte[] bytes, int index, int count);
override this.GetString : byte[] * int * int -> string
Public Overrides Function GetString (bytes As Byte(), index As Integer, count As Integer) As String

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

字串,包含將指定之位元組序列解碼的結果。

例外狀況

bytesnull

indexcount 小於零。

-或-

indexcount 不代表 bytes 中有效的範圍。

已啟用錯誤偵測,而且 bytes 包含無效的位元組序列。

(發生後援以取得詳細資訊,請參閱 .NET 中的字元編碼 ,以取得完整說明) 。

-和-

DecoderFallback 設定為 DecoderExceptionFallback

範例

下列範例會將字串編碼為兩個字節陣列,一個以小到尾的順序,另一個以大端順序編碼。 然後,它會將位元組譯碼回字串。

using System;
using System.Text;

public class Example  
{
   public static void Main()  
   {
      // Create two instances of UTF32Encoding: one with little-endian byte order and one with big-endian byte order.
      UTF32Encoding u32LE = new UTF32Encoding(false, true, true);
      UTF32Encoding u32BE = new UTF32Encoding(true, true, true);

      // Create byte arrays from the same 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 str = "za\u0306\u01FD\u03B2";

      // barrBE uses the big-endian byte order.
      byte[] barrBE = new byte[u32BE.GetByteCount(str)];
      u32BE.GetBytes(str, 0, str.Length, barrBE, 0);

      // barrLE uses the little-endian byte order.
      byte[] barrLE = new byte[u32LE.GetByteCount(str)];
      u32LE.GetBytes(str, 0, str.Length, barrLE, 0);

      // Decode the byte arrays.
      Console.WriteLine("BE array with BE encoding:");
      DisplayString(barrBE, u32BE);
      Console.WriteLine();

      Console.WriteLine("LE array with LE encoding:");
      DisplayString(barrLE, u32LE);
      Console.WriteLine();
   
      // Decode the byte arrays using an encoding with a different byte order.
      Console.WriteLine("BE array with LE encoding:");
      try  {
         DisplayString(barrBE, u32LE);
      }
      catch (System.ArgumentException e)  {
         Console.WriteLine(e.Message);
      }
      Console.WriteLine();

      Console.WriteLine("LE array with BE encoding:");
      try  {
         DisplayString(barrLE, u32BE);
      }
      catch (ArgumentException e)  {
         Console.WriteLine(e.Message);
      }
      Console.WriteLine();
   }

   public static void DisplayString(byte[] bytes, Encoding enc)  
   {
      // Display the name of the encoding used.
      Console.Write("{0,-25}: ", enc.ToString());

      // Decode the bytes and display the characters.
      Console.WriteLine(enc.GetString(bytes, 0, bytes.Length));
   }
}
// This example displays the following output:
//   BE array with BE encoding:
//   System.Text.UTF32Encoding: zăǽβ
//
//   LE array with LE encoding:
//   System.Text.UTF32Encoding: zăǽβ
//
//   BE array with LE encoding:
//   System.Text.UTF32Encoding: Unable to translate bytes [00][00][00][7A] at index 0 from specified code page to Unicode.
//
//   LE array with BE encoding:
//   System.Text.UTF32Encoding: Unable to translate bytes [7A][00][00][00] at index 0 from specified code page to Unicode.
Imports System.Text

Public Module Example  
   Public Sub Main()  
      ' Create two instances of UTF32Encoding: one with little-endian byte order and one with big-endian byte order.
      Dim u32LE As New UTF32Encoding(False, True, True)
      Dim u32BE As New UTF32Encoding(True, True, True)

      ' Create byte arrays from the same 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 str As String = "za" + ChrW(&h0306) + ChrW(&h01FD) + ChrW(&h03B2)

      ' barrBE uses the big-endian byte order.
      Dim barrBE(u32BE.GetByteCount(str) - 1) As Byte
      u32BE.GetBytes(str, 0, str.Length, barrBE, 0)

      ' barrLE uses the little-endian byte order.
      Dim barrLE(u32LE.GetByteCount(str) - 1) As Byte
      u32LE.GetBytes(str, 0, str.Length, barrLE, 0)

      ' Decode the byte arrays.
      Console.WriteLine("BE array with BE encoding:")
      DisplayString(barrBE, u32BE)
      Console.WriteLine()

      Console.WriteLine("LE array with LE encoding:")
      DisplayString(barrLE, u32LE)
      Console.WriteLine()
   
      ' Decode the byte arrays using an encoding with a different byte order.
      Console.WriteLine("BE array with LE encoding:")
      Try  
         DisplayString(barrBE, u32LE)
      Catch e As ArgumentException
         Console.WriteLine(e.Message)
      End Try
      Console.WriteLine()

      Console.WriteLine("LE array with BE encoding:")
      Try  
         DisplayString(barrLE, u32BE)
      Catch e As ArgumentException
         Console.WriteLine(e.Message)
      End Try
      Console.WriteLine()
   End Sub

   Public Sub DisplayString(bytes As Byte(), enc As Encoding )  
      ' Display the name of the encoding used.
      Console.Write("{0,-25}: ", enc.ToString())

      ' Decode the bytes and display the characters.
      Console.WriteLine(enc.GetString(bytes, 0, bytes.Length))
   End Sub
End Module
' This example displays the following output:
'   BE array with BE encoding:
'   System.Text.UTF32Encoding: zăǽβ
'
'   LE array with LE encoding:
'   System.Text.UTF32Encoding: zăǽβ
'
'   BE array with LE encoding:
'   System.Text.UTF32Encoding: Unable to translate bytes [00][00][00][7A] at index 0 from specified code page to Unicode.
'
'   LE array with BE encoding:
'   System.Text.UTF32Encoding: Unable to translate bytes [7A][00][00][00] at index 0 from specified code page to Unicode.

下列範例會呼叫 方法來初始化數位, GetByteCount 以判斷編碼字元串所需的位元組數目,然後將位元組順序標記的大小新增 (BOM) 。 然後,此範例會 GetPreamble 呼叫 方法,將 BOM 儲存至陣列,再呼叫 GetBytes 方法,以將編碼的位元組儲存至數位。 然後,此範例會 GetString 呼叫 方法來譯碼字串。

using System;
using System.Text;

public class Example
{
   public static void Main()
   {
      var utf32 = new UTF32Encoding(! BitConverter.IsLittleEndian, true);

      String s = "It was the best of times, it was the worst of times...";

      // We need to dimension the array, since we'll populate it with 2 method calls.
      Byte[] bytes = new Byte[utf32.GetByteCount(s) + utf32.GetPreamble().Length];
      // Encode the string.
      Array.Copy(utf32.GetPreamble(), bytes, utf32.GetPreamble().Length);
      utf32.GetBytes(s, 0, s.Length, bytes, utf32.GetPreamble().Length);

      // Decode the byte array.
      String s2 = utf32.GetString(bytes, 0, bytes.Length);
      Console.WriteLine(s2);
   }
}
// The example displays the following output:
//        ?It was the best of times, it was the worst of times...
Imports System.Text

Module Example
   Public Sub Main()
      Dim utf32 As New UTF32Encoding(Not BitConverter.IsLittleEndian, True)

      Dim s As String = "It was the best of times, it was the worst of times..."

      ' We need to dimension the array, since we'll populate it with 2 method calls.
      Dim bytes(utf32.GetByteCount(s) + utf32.GetPreamble().Length - 1) As Byte
      ' Encode the string.
      Array.Copy(utf32.GetPreamble(), bytes, utf32.GetPreamble().Length)
      utf32.GetBytes(s, 0, s.Length, bytes, utf32.GetPreamble().Length)

      ' Decode the byte array.
      Dim s2 As String = utf32.GetString(bytes, 0, bytes.Length)
      Console.WriteLine(s2)
   End Sub
End Module
' The example displays the following output:
'       ?It was the best of times, it was the worst of times...

請注意,在此情況下,譯碼的字串與原始字串不同,因為它以32位位元組順序標記U+FFFE U+0000開頭。 這表示這兩個字串會比較為不相等,而且如果字串是輸出,則 BOM 會顯示為取代字元 “?”。

備註

發生錯誤偵測時,無效的序列會導致這個方法擲回 ArgumentException。 若未偵測錯誤,則會忽略無效的序列,而且不會擲回例外狀況。

如果要譯碼的位元組範圍包含位元組順序標記 (BOM) ,且位元組陣列是由非 BOM 感知類型的方法傳回,則這個方法所傳回的字元 U+FFFE 會包含在傳回的字元數位中。 您可以呼叫 String.TrimStart 方法來移除它。

要轉換的數據,例如從數據流讀取的數據,可能只能在循序區塊中使用。 在此情況下,或者,如果資料量太大,因此需要分成較小的區塊,應用程式應該分別使用 DecoderEncoder 方法或 方法所提供的 GetDecoderGetEncoder

適用於

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