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System.Text Namespace

Updated: April 2011

The System.Text namespace contains classes that represent ASCII and Unicode character encodings; abstract base classes for converting blocks of characters to and from blocks of bytes; and a helper class that manipulates and formats String objects without creating intermediate instances of String.

The encoding classes are primarily intended to convert between different encodings or code pages and a Unicode encoding. Encoding.Unicode (UTF-16) encoding is used internally by the .NET Framework, and Encoding.UTF8 encoding is often used for storing character data to ensure portability across machines and cultures.

The classes derived from Encoding enable you to choose a fallback strategy, which determines how characters that cannot be encoded into a sequence of bytes, or bytes that cannot be decoded into characters, are handled. You can choose one of the following:

  • Exception fallback. You can choose to throw exceptions on data errors either by using a throwonerror flag that is available in some class constructors or by using the EncoderExceptionFallback and DecoderExceptionFallback classes. If you are concerned about the integrity of the data stream, throwing on an exception is recommended.

  • Replacement fallback. You can use the EncoderFallback and DecoderFallback classes to silently change a character to "?" or to the Unicode replacement character (U+FFFD).

  • Best-fit fallback. This option maps a character in one encoding to a character in another encoding. Best fit fallback is often not recommended because it can cause data loss and confusion, and is slower than simple "?" character replacements. However, for ANSI code pages the best-fit behavior is the default.

The StringBuilder class is designed for operations that perform extensive manipulations on a single string. Unlike the String class, the StringBuilder class is mutable and provides better performance when concatenating or deleting strings.

For more information about System.Text, see Character Encoding in the .NET Framework and the MSDN blog Shawn Steele's Thoughts about Windows and .NET Framework Globalization APIs.

  ClassDescription
Public classASCIIEncodingRepresents an ASCII character encoding of Unicode characters.
Public classDecoderConverts a sequence of encoded bytes into a set of characters.
Public classDecoderExceptionFallbackThrows DecoderFallbackException if an encoded input byte sequence cannot be converted to a decoded output character. This class cannot be inherited.
Public classDecoderExceptionFallbackBufferThrows DecoderFallbackException when an encoded input byte sequence cannot be converted to a decoded output character. This class cannot be inherited.
Public classDecoderFallbackProvides a failure-handling mechanism, called a fallback, for an encoded input byte sequence that cannot be converted to an output character.
Public classDecoderFallbackBufferProvides a buffer that allows a fallback handler to return an alternate string to a decoder when it cannot decode an input byte sequence.
Public classDecoderFallbackExceptionThe exception that is thrown when a decoder fallback operation fails. This class cannot be inherited.
Public classDecoderReplacementFallbackProvides a failure-handling mechanism, called a fallback, for an encoded input byte sequence that cannot be converted to an output character. The fallback emits a user-specified replacement string instead of a decoded input byte sequence. This class cannot be inherited.
Public classDecoderReplacementFallbackBufferRepresents a substitute output string that is emitted when the original input byte sequence cannot be decoded. This class cannot be inherited.
Public classEncoderConverts a set of characters into a sequence of bytes.
Public classEncoderExceptionFallbackThrows a EncoderFallbackException if an input character cannot be converted to an encoded output byte sequence. This class cannot be inherited.
Public classEncoderExceptionFallbackBufferThrows EncoderFallbackException when an input character cannot be converted to an encoded output byte sequence. This class cannot be inherited.
Public classEncoderFallbackProvides a failure-handling mechanism, called a fallback, for an input character that cannot be converted to an encoded output byte sequence.
Public classEncoderFallbackBufferProvides a buffer that allows a fallback handler to return an alternate string to an encoder when it cannot encode an input character.
Public classEncoderFallbackExceptionThe exception that is thrown when an encoder fallback operation fails. This class cannot be inherited.
Public classEncoderReplacementFallbackProvides a failure handling mechanism, called a fallback, for an input character that cannot be converted to an output byte sequence. The fallback uses a user-specified replacement string instead of the original input character. This class cannot be inherited.
Public classEncoderReplacementFallbackBufferRepresents a substitute input string that is used when the original input character cannot be encoded. This class cannot be inherited.
Public classEncodingRepresents a character encoding.
Public classEncodingInfoProvides basic information about an encoding.
Public classStringBuilderRepresents a mutable string of characters. This class cannot be inherited.
Public classUnicodeEncodingRepresents a UTF-16 encoding of Unicode characters.
Public classUTF32EncodingRepresents a UTF-32 encoding of Unicode characters.
Public classUTF7EncodingRepresents a UTF-7 encoding of Unicode characters.
Public classUTF8EncodingRepresents a UTF-8 encoding of Unicode characters.

  EnumerationDescription
Public enumerationNormalizationFormDefines the type of normalization to perform.

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April 2011

Expanded the summary.

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