When overridden in a derived class, generates and writes the surrogate character entity for the surrogate character pair.
Assemblies: System.Xml (in System.Xml.dll)
System.Xml.ReaderWriter (in System.Xml.ReaderWriter.dll)
An invalid surrogate character pair was passed.
An XmlWriter method was called before a previous asynchronous operation finished. In this case, InvalidOperationException is thrown with the message “An asynchronous operation is already in progress.”
This method is only applicable on systems that use UTF-16 encoding.
The surrogate character entity is written in hexadecimal format. The range for surrogate characters is #x10000 to #x10FFFF. The following formula is used to generate the surrogate character entity: (highChar -0xD800) * 0x400 + (lowChar -0xDC00) + 0x10000
For both HTML and XML, the document character set (and therefore the notation of numeric character references) is based on UCS [ISO-10646]. A single numeric character reference in a source document may therefore in some cases correspond to two 16-bit units in a string (a high surrogate and a low surrogate). These 16-bit units are referred to as a surrogate pair.
For more information regarding surrogates or characters, refer to section 3.7 of the Unicode 3.0/Unicode 2.0 standard located at http://www.unicode.org, or section 2.2 of the W3C XML 1.0 Recommendation located at http://www.w3.org/TR/REC-xml#charsets.
For the asynchronous version of this method, see WriteSurrogateCharEntityAsync.