UTF-8 encodes Unicode characters with a variable number of bytes per character. This encoding is optimized for the lower 127 ASCII characters, yielding an efficient mechanism to encode English in an internationalizable way. The UTF-8 identifier is the Unicode byte order mark (0xFEFF) written in UTF-8 (0xEF 0xBB 0xBF). The byte order mark is used to distinguish UTF-8 text from other encodings.

This class offers an error-checking feature that can be turned on when an instance of the class is constructed. Certain methods in this class check for invalid sequences of surrogate pairs. If error-checking is turned on and an invalid sequence is detected, ArgumentException is thrown. If error-checking is not turned on and an invalid sequence is detected, no exception is thrown and execution continues in a method-defined manner. For more information regarding surrogate pairs, see System.Globalization.UnicodeCategory .