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UTF8Encoding Class

UTF8Encoding Class

Represents a UTF-8 encoding of Unicode characters.

Namespace:  System.Text
Assemblies:   System.Text.Encoding.Extensions (in System.Text.Encoding.Extensions.dll)
  mscorlib (in mscorlib.dll)

public class UTF8Encoding : Encoding

The UTF8Encoding type exposes the following members.

  NameDescription
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryUTF8Encoding()Initializes a new instance of the UTF8Encoding class.
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryUTF8Encoding(Boolean)Initializes a new instance of the UTF8Encoding class. A parameter specifies whether to provide a Unicode byte order mark.
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryUTF8Encoding(Boolean, Boolean)Initializes a new instance of the UTF8Encoding class. Parameters specify whether to provide a Unicode byte order mark and whether to throw an exception when an invalid encoding is detected.
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  NameDescription
Public propertyBodyNameWhen overridden in a derived class, gets a name for the current encoding that can be used with mail agent body tags. (Inherited from Encoding.)
Public propertySupported by the XNA FrameworkCodePageWhen overridden in a derived class, gets the code page identifier of the current Encoding. (Inherited from Encoding.)
Public propertyDecoderFallbackGets or sets the DecoderFallback object for the current Encoding object. (Inherited from Encoding.)
Public propertyEncoderFallbackGets or sets the EncoderFallback object for the current Encoding object. (Inherited from Encoding.)
Public propertyEncodingNameWhen overridden in a derived class, gets the human-readable description of the current encoding. (Inherited from Encoding.)
Public propertyHeaderNameWhen overridden in a derived class, gets a name for the current encoding that can be used with mail agent header tags. (Inherited from Encoding.)
Public propertyIsBrowserDisplayWhen overridden in a derived class, gets a value indicating whether the current encoding can be used by browser clients for displaying content. (Inherited from Encoding.)
Public propertyIsBrowserSaveWhen overridden in a derived class, gets a value indicating whether the current encoding can be used by browser clients for saving content. (Inherited from Encoding.)
Public propertyIsMailNewsDisplayWhen overridden in a derived class, gets a value indicating whether the current encoding can be used by mail and news clients for displaying content. (Inherited from Encoding.)
Public propertyIsMailNewsSaveWhen overridden in a derived class, gets a value indicating whether the current encoding can be used by mail and news clients for saving content. (Inherited from Encoding.)
Public propertyIsReadOnlyWhen overridden in a derived class, gets a value indicating whether the current encoding is read-only. (Inherited from Encoding.)
Public propertyIsSingleByteWhen overridden in a derived class, gets a value indicating whether the current encoding uses single-byte code points. (Inherited from Encoding.)
Public propertySupported by the XNA FrameworkSupported by Portable Class LibraryWebNameWhen overridden in a derived class, gets the name registered with the Internet Assigned Numbers Authority (IANA) for the current encoding. (Inherited from Encoding.)
Public propertyWindowsCodePageWhen overridden in a derived class, gets the Windows operating system code page that most closely corresponds to the current encoding. (Inherited from Encoding.)
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  NameDescription
Public methodSupported by the XNA FrameworkCloneWhen overridden in a derived class, creates a shallow copy of the current Encoding object. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryEqualsDetermines whether the specified object is equal to the current UTF8Encoding object. (Overrides Encoding.Equals(Object).)
Protected methodSupported by the XNA FrameworkSupported by Portable Class LibraryFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetByteCount(Char[])When overridden in a derived class, calculates the number of bytes produced by encoding all the characters in the specified character array. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetByteCount(String)Calculates the number of bytes produced by encoding the characters in the specified String. (Overrides Encoding.GetByteCount(String).)
Public methodGetByteCount(Char*, Int32)Calculates the number of bytes produced by encoding a set of characters starting at the specified character pointer. (Overrides Encoding.GetByteCount(Char*, Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetByteCount(Char[], Int32, Int32)Calculates the number of bytes produced by encoding a set of characters from the specified character array. (Overrides Encoding.GetByteCount(Char[], Int32, Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetBytes(Char[])When overridden in a derived class, encodes all the characters in the specified character array into a sequence of bytes. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkGetBytes(String)When overridden in a derived class, encodes all the characters in the specified string into a sequence of bytes. (Inherited from Encoding.)

In XNA Framework, this member is overridden by GetBytes(String).
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetBytes(Char[], Int32, Int32)When overridden in a derived class, encodes a set of characters from the specified character array into a sequence of bytes. (Inherited from Encoding.)
Public methodGetBytes(Char*, Int32, Byte*, Int32)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. (Overrides Encoding.GetBytes(Char*, Int32, Byte*, Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetBytes(Char[], Int32, Int32, Byte[], Int32)Encodes a set of characters from the specified character array into the specified byte array. (Overrides Encoding.GetBytes(Char[], Int32, Int32, Byte[], Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetBytes(String, Int32, Int32, Byte[], Int32)Encodes a set of characters from the specified String into the specified byte array. (Overrides Encoding.GetBytes(String, Int32, Int32, Byte[], Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetCharCount(Byte[])When overridden in a derived class, calculates the number of characters produced by decoding all the bytes in the specified byte array. (Inherited from Encoding.)
Public methodGetCharCount(Byte*, Int32)Calculates the number of characters produced by decoding a sequence of bytes starting at the specified byte pointer. (Overrides Encoding.GetCharCount(Byte*, Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetCharCount(Byte[], Int32, Int32)Calculates the number of characters produced by decoding a sequence of bytes from the specified byte array. (Overrides Encoding.GetCharCount(Byte[], Int32, Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetChars(Byte[])When overridden in a derived class, decodes all the bytes in the specified byte array into a set of characters. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetChars(Byte[], Int32, Int32)When overridden in a derived class, decodes a sequence of bytes from the specified byte array into a set of characters. (Inherited from Encoding.)
Public methodGetChars(Byte*, Int32, Char*, Int32)Decodes a sequence of bytes starting at the specified byte pointer into a set of characters that are stored starting at the specified character pointer. (Overrides Encoding.GetChars(Byte*, Int32, Char*, Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetChars(Byte[], Int32, Int32, Char[], Int32)Decodes a sequence of bytes from the specified byte array into the specified character array. (Overrides Encoding.GetChars(Byte[], Int32, Int32, Char[], Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetDecoderObtains a decoder that converts a UTF-8 encoded sequence of bytes into a sequence of Unicode characters. (Overrides Encoding.GetDecoder().)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetEncoderObtains an encoder that converts a sequence of Unicode characters into a UTF-8 encoded sequence of bytes. (Overrides Encoding.GetEncoder().)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetHashCodeReturns the hash code for the current instance. (Overrides Encoding.GetHashCode().)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetMaxByteCountCalculates the maximum number of bytes produced by encoding the specified number of characters. (Overrides Encoding.GetMaxByteCount(Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetMaxCharCountCalculates the maximum number of characters produced by decoding the specified number of bytes. (Overrides Encoding.GetMaxCharCount(Int32).)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetPreambleReturns a Unicode byte order mark encoded in UTF-8 format, if the UTF8Encoding encoding object is configured to supply one. (Overrides Encoding.GetPreamble().)
Public methodGetString(Byte[])When overridden in a derived class, decodes all the bytes in the specified byte array into a string. (Inherited from Encoding.)
Public methodGetString(Byte*, Int32)When overridden in a derived class, decodes a specified number of bytes starting at a specified address into a string. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkGetString(Byte[], Int32, Int32)Decodes a range of bytes from a byte array into a string. (Overrides Encoding.GetString(Byte[], Int32, Int32).)

In XNA Framework 3.0, this member is inherited from Encoding.GetString(Byte[], Int32, Int32).
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodIsAlwaysNormalized()Gets a value indicating whether the current encoding is always normalized, using the default normalization form. (Inherited from Encoding.)
Public methodIsAlwaysNormalized(NormalizationForm)When overridden in a derived class, gets a value indicating whether the current encoding is always normalized, using the specified normalization form. (Inherited from Encoding.)
Protected methodSupported by the XNA FrameworkSupported by Portable Class LibraryMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryToStringReturns 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. Decoding is the process of transforming a sequence of encoded bytes into a set of Unicode characters.

UTF-8 is a Unicode encoding that represents each code point as a sequence of one to four bytes. Unlike the UTF-16 and UTF-32 encodings, the UTF-8 encoding does not require "endianness"; the encoding scheme is the same regardless of whether the processor is big-endian or little-endian. UTF8Encoding corresponds to the Windows code page 65001. For more information about the UTFs and other encodings supported by System.Text, see Character Encoding in the .NET Framework.

You can instantiate a UTF8Encoding object in a number of ways, depending on whether you want to it to provide a byte order mark (BOM) and whether you want to enable error detection. The following table lists the constructors and the Encoding property that return a UTF8Encoding object.

Member

BOM

Error detection

Encoding.UTF8

Yes

No (Replacement fallback)

UTF8Encoding.UTF8Encoding()

No

No (Replacement fallback)

UTF8Encoding.UTF8Encoding(Boolean)

Configurable

No (Replacement fallback)

UTF8Encoding.UTF8Encoding(Boolean, Boolean)

Configurable

Configurable

The GetByteCount method determines how many bytes result in encoding a set of Unicode characters, and the GetBytes method performs the actual encoding.

Likewise, the GetCharCount method determines how many characters result in decoding a sequence of bytes, and the GetChars and GetString methods perform the actual decoding.

For an encoder or decoder that is able to save state information when encoding or decoding data that spans multiple blocks (such as string of 1 million characters that is encoded in 100,000-character segments), use the GetEncoder and GetDecoder properties, respectively.

Optionally, the UTF8Encoding object provides a byte order mark (BOM), which is an array of bytes that can be prefixed to the beginning of the byte stream that results from the encoding process. If a UTF-8 encoded byte stream is prefaced with a byte order mark (BOM), it helps the decoder determine the byte order and the transformation format or UTF. Note, however, that the Unicode Standard neither requires nor recommends a BOM in UTF-8 encoded streams. For more information on byte order and the byte order mark, see The Unicode Standard at the Unicode home page.

If the encoder is configured to provide a BOM, you can retrieve it by calling the GetPreamble method; otherwise, the method returns an empty array. Note that, even if a UTF8Encoding object is configured for BOM support, you must include the BOM at the beginning of the encoded byte stream as appropriate; the encoding methods of the UTF8Encoding class do not do this automatically.

NoteNote

To enable error detection and to make the class instance more secure, you should call the UTF8Encoding(Boolean, Boolean) constructor and set the throwOnInvalidBytes parameter to true. With error detection enabled, a method that detects an invalid sequence of characters or bytes throws an ArgumentException exception. Without error detection, no exception is thrown, and the invalid sequence is generally ignored.

NoteNote

The state of a UTF-8 encoded object is not preserved if the object is serialized and deserialized using different .NET Framework versions.

The following example uses a UTF8Encoding object to encode a string of Unicode characters and store them in a byte array. The Unicode string includes two characters, Pi (U+03A0) and Sigma (U+03A3), that are outside the ASCII character range. When the encoded byte array is decoded back to a string, the Pi and Sigma characters are still present.

using System;
using System.Text;

class Example
{
    public static void Main()
    {
        // Create a UTF-8 encoding.
        UTF8Encoding utf8 = new UTF8Encoding();

        // A Unicode string with two characters outside an 8-bit code range.
        String unicodeString =
            "This Unicode string has 2 characters outside the " +
            "ASCII range:\n" +
            "Pi (\u03a0), and Sigma (\u03a3).";
        Console.WriteLine("Original string:");
        Console.WriteLine(unicodeString);

        // Encode the string.
        Byte[] encodedBytes = utf8.GetBytes(unicodeString);
        Console.WriteLine();
        Console.WriteLine("Encoded bytes:");
        for (int ctr = 0; ctr < encodedBytes.Length; ctr++) {
            Console.Write("{0:X2} ", encodedBytes[ctr]);
            if ((ctr + 1) %  25 == 0)
               Console.WriteLine();
        }
        Console.WriteLine();

        // Decode bytes back to string.
        String decodedString = utf8.GetString(encodedBytes);
        Console.WriteLine();
        Console.WriteLine("Decoded bytes:");
        Console.WriteLine(decodedString);
    }
}
// The example displays the following output: 
//    Original string: 
//    This Unicode string has 2 characters outside the ASCII range: 
//    Pi (π), and Sigma (Σ). 
// 
//    Encoded bytes: 
//    54 68 69 73 20 55 6E 69 63 6F 64 65 20 73 74 72 69 6E 67 20 68 61 73 20 32 
//    20 63 68 61 72 61 63 74 65 72 73 20 6F 75 74 73 69 64 65 20 74 68 65 20 41 
//    53 43 49 49 20 72 61 6E 67 65 3A 20 0D 0A 50 69 20 28 CE A0 29 2C 20 61 6E 
//    64 20 53 69 67 6D 61 20 28 CE A3 29 2E 
// 
//    Decoded bytes: 
//    This Unicode string has 2 characters outside the ASCII range: 
//    Pi (π), and Sigma (Σ).

The following example uses the same string as the previous example, except that it writes the encoded bytes to a file and prefixes the byte stream with a byte order mark (BOM). It then reads the file in two different ways: as a text file by using a StreamReader object; and as a binary file. As you would expect, in neither case is the BOM included in the newly read string.

using System;
using System.IO;
using System.Text;

public class Example
{
   public static void Main()
   {
        // Create a UTF-8 encoding that supports a BOM.
        Encoding utf8 = new UTF8Encoding(true);

        // A Unicode string with two characters outside an 8-bit code range.
        String unicodeString =
            "This Unicode string has 2 characters outside the " +
            "ASCII range:\n" +
            "Pi (\u03A0)), and Sigma (\u03A3).";
        Console.WriteLine("Original string:");
        Console.WriteLine(unicodeString);
        Console.WriteLine();

        // Encode the string.
        Byte[] encodedBytes = utf8.GetBytes(unicodeString);
        Console.WriteLine("The encoded string has {0} bytes.",
                          encodedBytes.Length);
        Console.WriteLine();

        // Write the bytes to a file with a BOM. 
        var fs = new FileStream(@".\UTF8Encoding.txt", FileMode.Create);
        Byte[] bom = utf8.GetPreamble();
        fs.Write(bom, 0, bom.Length);
        fs.Write(encodedBytes, 0, encodedBytes.Length);
        Console.WriteLine("Wrote {0} bytes to the file.", fs.Length);
        fs.Close();
        Console.WriteLine();

        // Open the file using StreamReader. 
        var sr = new StreamReader(@".\UTF8Encoding.txt");
        String newString = sr.ReadToEnd();
        sr.Close();
        Console.WriteLine("String read using StreamReader:");
        Console.WriteLine(newString);
        Console.WriteLine();

        // Open the file as a binary file and decode the bytes back to a string.
        fs = new FileStream(@".\UTF8Encoding.txt", FileMode.Open);
        Byte[] bytes = new Byte[fs.Length];
        fs.Read(bytes, 0, (int)fs.Length);
        fs.Close();

        String decodedString = utf8.GetString(encodedBytes);
        Console.WriteLine("Decoded bytes:");
        Console.WriteLine(decodedString);
   }
}
// The example displays the following output: 
//    Original string: 
//    This Unicode string has 2 characters outside the ASCII range: 
//    Pi (π), and Sigma (Σ). 
// 
//    The encoded string has 88 bytes. 
// 
//    Wrote 91 bytes to the file. 
// 
//    String read using StreamReader: 
//    This Unicode string has 2 characters outside the ASCII range: 
//    Pi (π), and Sigma (Σ). 
// 
//    Decoded bytes: 
//    This Unicode string has 2 characters outside the ASCII range: 
//    Pi (π), and Sigma (Σ).

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Portable Class Library

Supported in: Portable Class Library

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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