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Encoding Class

Represents a character encoding.

Namespace:  System.Text
Assembly:  mscorlib (in mscorlib.dll)

[ComVisibleAttribute(true)]
public abstract class Encoding

The Encoding type exposes the following members.

  NameDescription
Protected methodSupported by Silverlight for Windows PhoneSupported by Xbox 360EncodingInitializes a new instance of the Encoding class.
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  NameDescription
Public propertyStatic memberSupported by Silverlight for Windows PhoneSupported by Xbox 360BigEndianUnicodeGets an encoding for the UTF-16 format that uses the big-endian byte order.
Public propertyStatic memberSupported by Silverlight for Windows PhoneSupported by Xbox 360UnicodeGets an encoding for the UTF-16 format using the little-endian byte order.
Public propertyStatic memberSupported by Silverlight for Windows PhoneSupported by Xbox 360UTF8Gets an encoding for the UTF-8 format.
Public propertySupported by Silverlight for Windows PhoneSupported by Xbox 360WebNameWhen overridden in a derived class, gets the name registered with the Internet Assigned Numbers Authority (IANA) for the current encoding.
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  NameDescription
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360CloneWhen overridden in a derived class, creates a shallow copy of the current Encoding object.
Public methodStatic memberSupported by Silverlight for Windows PhoneSupported by Xbox 360Convert(Encoding, Encoding, Byte[])Converts an entire byte array from one encoding to another.
Public methodStatic memberSupported by Silverlight for Windows PhoneSupported by Xbox 360Convert(Encoding, Encoding, Byte[], Int32, Int32)Converts a range of bytes in a byte array from one encoding to another.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360EqualsDetermines whether the specified Object is equal to the current instance. (Overrides Object.Equals(Object).)
Protected methodSupported by Silverlight for Windows PhoneSupported by Xbox 360FinalizeAllows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetByteCount(Char[])When overridden in a derived class, calculates the number of bytes produced by encoding all the characters in the specified character array.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetByteCount(String)When overridden in a derived class, calculates the number of bytes produced by encoding the characters in the specified string.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetByteCount(Char[], Int32, Int32)When overridden in a derived class, calculates the number of bytes produced by encoding a set of characters from the specified character array.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetBytes(Char[])When overridden in a derived class, encodes all the characters in the specified character array into a sequence of bytes.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetBytes(String)When overridden in a derived class, encodes all the characters in the specified string into a sequence of bytes.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetBytes(Char[], Int32, Int32)When overridden in a derived class, encodes a set of characters from the specified character array into a sequence of bytes.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetBytes(Char*, Int32, Byte*, Int32)Security Critical. When overridden in a derived class, encodes a set of characters starting at the specified character pointer into a sequence of bytes that are stored starting at the specified byte pointer.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetBytes(Char[], Int32, Int32, Byte[], Int32)When overridden in a derived class, encodes a set of characters from the specified character array into the specified byte array.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetBytes(String, Int32, Int32, Byte[], Int32)When overridden in a derived class, encodes a set of characters from the specified string into the specified byte array.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetCharCount(Byte[])When overridden in a derived class, calculates the number of characters produced by decoding all the bytes in the specified byte array.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetCharCount(Byte[], Int32, Int32)When overridden in a derived class, calculates the number of characters produced by decoding a sequence of bytes from the specified byte array.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetChars(Byte[])When overridden in a derived class, decodes all the bytes in the specified byte array into a set of characters.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetChars(Byte[], Int32, Int32)When overridden in a derived class, decodes a sequence of bytes from the specified byte array into a set of characters.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetChars(Byte[], Int32, Int32, Char[], Int32)When overridden in a derived class, decodes a sequence of bytes from the specified byte array into the specified character array.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetDecoderWhen overridden in a derived class, obtains a decoder that converts an encoded sequence of bytes into a sequence of characters.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetEncoderWhen overridden in a derived class, obtains an encoder that converts a sequence of Unicode characters into an encoded sequence of bytes.
Public methodStatic memberSupported by Silverlight for Windows PhoneSupported by Xbox 360GetEncodingReturns the encoding associated with the specified name.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetHashCodeReturns the hash code for the current instance. (Overrides Object.GetHashCode().)
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetMaxByteCountWhen overridden in a derived class, calculates the maximum number of bytes produced by encoding the specified number of characters.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetMaxCharCountWhen overridden in a derived class, calculates the maximum number of characters produced by decoding the specified number of bytes.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetPreambleWhen overridden in a derived class, returns a sequence of bytes that specifies the encoding used.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetStringWhen overridden in a derived class, decodes a sequence of bytes from the specified byte array into a string.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodSupported by Silverlight for Windows PhoneSupported by Xbox 360MemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360ToStringReturns a string that represents the current object. (Inherited from Object.)
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Encoding is the process of transforming a set of Unicode characters into a sequence of bytes. In contrast, decoding is the process of transforming a sequence of encoded bytes into a set of Unicode characters. The .NET Framework for Silverlight supports two encoding methods: UTF8, in which a single character is encoded in one to four bytes; and UTF16 or Unicode, in which a single character is represented as either a two-byte or a four-byte value. Because Encoding is the base class for all encodings, it can also be derived from to create custom encodings for the .NET Framework for Silverlight.

The .NET Framework for Silverlight includes the following implementations of the Encoding class to support Unicode encoding:

  • The UTF8Encoding class, which uses UTF8 encoding to represent a single character in one to four bytes. A class instance is also available through the UTF8 property.

  • The UnicodeEncoding class, which uses UTF16 encoding to represent a single character as either a two-byte or a four-byte value. Both little-endian and big-endian byte orders are supported. These encoders are also available through the Unicode property and the BigEndianUnicode property, respectively.

The Encoding class is primarily intended to convert between these three different Unicode encodings. In addition, you can derive from the Encoding class to create a custom encoding that is not supported by the .NET Framework for Silverlight.

NoteNote:

If you require an encoding that is not present in the .NET Framework for Silverlight, you can also use ASP.NET and the .NET Framework to perform the encoding or decoding on a Web server.

Your applications can instantiate an encoding object that represents a specific encoding in several ways:

  • By calling one of the overloads of that encoding's class constructor.

  • By retrieving the value of the BigEndianUnicode, Unicode, or UTF8 properties, depending on the encoding desired.

  • By calling the GetEncoding method with the name of an encoding to obtain that encoding.

The GetByteCount method determines how many bytes result from encoding a set of Unicode characters, and the GetBytes method performs the actual encoding. The Encoding.GetBytes method expects discrete conversions (that is, each method call converts the bytes passed to it without including the unconverted bytes from the previous method call). In contrast, the GetBytes method, because it preserves state between method calls, can decode a single input stream in multiple method calls.

Several versions of GetByteCount and GetBytes are supported. The following are some programming considerations for using these methods:

  • The application might need to encode a stream, such as an input stream from the user. This can be done by using multiple calls to the GetBytes method because it maintains state between calls.

  • For string input, you should call the overloads of the GetBytes method that encode the strings passed to them.

  • If your application must convert a large amount of data, it should reuse the output buffer. In this case, the GetBytes version that supports byte arrays is the best choice.

  • Consider using the Encoder.Convert method instead of GetByteCount. The conversion method converts as much data as possible, and throws an exception if the output buffer is too small. For continuous encoding of a stream, this method is often the best choice.

The GetCharCount method determines how many characters result from decoding a sequence of bytes, and the Encoding.GetChars method performs the actual decoding. The Encoding.GetChars method expects discrete conversions (that is, it treats each method call independently of the previous method call). In contrast, the GetChars method preserves state so that it can decode undecoded bytes from the previous method call. This makes it suitable for decoding a stream of bytes.

Several versions of GetCharCount and GetChars are supported. The following are some programming considerations for use of these methods:

  • The application might need to decode multiple input bytes and process the bytes using multiple calls. In this case, your application probably needs to maintain state between calls.

  • If the application handles string outputs, it is recommended to use the GetString method. Since this method must check string length and allocate a buffer, it is slightly slower, but the resulting String type is to be preferred.

  • If your application must convert a large amount of data, it should reuse the output buffer. In this case, the Encoding.GetChars(Byte[], Int32, Int32, Char[], Int32) version that supports output character buffers is the best choice.

  • Consider using the Decoder.Convert method instead of GetCharCount. The conversion method converts as much data as possible and throws an exception if the output buffer is too small. For continuous decoding of a stream, this method is often the best choice.

If the data to be converted is available only in sequential blocks (such as data read from a stream) or if the amount of data is so large that it needs to be divided into smaller blocks, your application should use the Decoder or the Encoder provided by the GetDecoder method or the GetEncoder method, respectively, of a derived class.

The UTF-16 encoder can use the big-endian byte order (most significant byte first) or the little-endian byte order (least significant byte first). For example, the Latin Capital Letter A (U+0041) is encoded as follows (in hexadecimal):

  • UTF-16 big-endian byte order: 00 41

  • UTF-16 little-endian byte order: 41 00

It is generally more efficient to store Unicode characters using the native byte order. For example, it is better to use the little-endian byte order on little-endian platforms, such as Intel computers, and the big-endian order on big-endian platforms.

The GetPreamble method retrieves an array of bytes that includes the byte order mark (BOM). If this byte array is prefixed to an encoded stream, it helps the decoder to identify the encoding format used.

For more information on byte order and the byte order mark, see The Unicode Standard at the Unicode home page.

The following code example converts a string from one encoding to another.


using System;
using System.Text;

class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      string unicodeString = "This string contains the unicode character Pi (\u03a0)";

      // Create two different encodings.
      Encoding utf8 = Encoding.UTF8;
      Encoding unicode = Encoding.Unicode;

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

      // Perform the conversion from one encoding to the other.
      byte[] utf8Bytes = Encoding.Convert(unicode, utf8, unicodeBytes);

      // Convert the new byte[] into a char[] and then into a string.
      char[] utf8Chars = new char[utf8.GetCharCount(utf8Bytes, 0, utf8Bytes.Length)];
      utf8.GetChars(utf8Bytes, 0, utf8Bytes.Length, utf8Chars, 0);
      string utf8String = new string(utf8Chars);

      // Display the strings created before and after the conversion.
      outputBlock.Text += String.Format("Original string: {0}", unicodeString) + "\n";
      outputBlock.Text += String.Format("Ascii converted string: {0}", utf8String) + "\n";
   }
}
// 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 (?)


Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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