UnicodeEncoding.GetString(Byte[], Int32, Int32) Method

Definition

Namespace:

System.Text

Assembly:

System.Text.Encoding.Extensions.dll

Source:

UnicodeEncoding.cs

Decodes a range of bytes from a byte array into a string.

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

Parameters

bytes

Byte[]

The byte array containing the sequence of bytes to decode.

index

Int32

The index of the first byte to decode.

count

Int32

The number of bytes to decode.

Returns

String

A String object containing the results of decoding the specified sequence of bytes.

Exceptions

ArgumentNullException

bytes is null (Nothing).

ArgumentOutOfRangeException

index or count is less than zero.

-or-

index and count do not denote a valid range in bytes.

ArgumentException

Error detection is enabled, and bytes contains an invalid sequence of bytes.

DecoderFallbackException

A fallback occurred (for more information, see Character Encoding in .NET)

-and-

DecoderFallback is set to DecoderExceptionFallback.

Examples

The following example initializes an array by calling the GetByteCount method to determine exactly how many bytes are required for an encoded string and then adding the size of the byte order mark (BOM). The example then calls the GetPreamble method to store the BOM to the array before calling the GetBytes method to store the encoded bytes to the array. The example then calls the GetString method to decode the string.

using System;
using System.Text;

public class Example
{
   public static void Main()
   {
      UTF8Encoding utf8 = new UTF8Encoding(true, 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[utf8.GetByteCount(s) + utf8.GetPreamble().Length];
      // Encode the string.
      Array.Copy(utf8.GetPreamble(), bytes, utf8.GetPreamble().Length);
      utf8.GetBytes(s, 0, s.Length, bytes, utf8.GetPreamble().Length);

      // Decode the byte array.
      String s2 = utf8.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 utf8 As New UTF8Encoding(True, 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(utf8.GetByteCount(s) + utf8.GetPreamble().Length - 1) As Byte
      ' Encode the string.
      Array.Copy(utf8.GetPreamble(), bytes, utf8.GetPreamble().Length)
      utf8.GetBytes(s, 0, s.Length, bytes, utf8.GetPreamble().Length)

      ' Decode the byte array.
      Dim s2 As String = utf8.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...

Note that in this case the decoded string differs from the original string, since it begins with a 16-bit byte order mark U+FFFD. This means that the two strings will compare as unequal, and that if the string is output, the BOM will be displayed as the replacement character "?". To remove the BOM at the beginning of the string, you can call the String.TrimStart method.

Remarks

With error detection, an invalid sequence causes this method to throw a ArgumentException. Without error detection, invalid sequences are ignored, and no exception is thrown.

If the range of bytes to be decoded includes the byte order mark (BOM) and the byte array was returned by a method of a non-BOM aware type, the character U+FFFE is included in the character array returned by this method. You can remove it by calling the String.TrimStart method.

Data to be converted, such as data read from a stream, might be available only in sequential blocks. In this case, or if the amount of data is so large that it needs to be divided into smaller blocks, the application should use the Decoder or the Encoder object provided by the GetDecoder or the GetEncoder method, respectively.

See also

• GetChars(Byte[], Int32, Int32, Char[], Int32)
• GetDecoder()
• GetCharCount(Byte[], Int32, Int32)
• GetMaxCharCount(Int32)