C# Regular Expressions with \Uxxxxxxxx characters in the pattern

Question

Regex.IsMatch( \"foo\", \"[\\U00010000-\\U0010FFFF]\" ) 

Throws: System.ArgumentException: parsing \"[-]\" - [x-y] range in reverse order.

Answer 1

To workaround such things with .Net regex engine, I'm using following trick: "[\U010000-\U10FFFF]" is replaced with [\uD800-\uDBFF][\uDC00-\uDFFF] The idea behind this is that as .Net regexes handle code units instead of code points, we're providing it with surrogate ranges as regular characters. It's also possible to specify more narrow ranges by operating with edges, e.g.: [\U011DEF-\U013E07] is same as (?:\uD807[\uDDEF-\uDFFF])|(?:[\uD808-\uD80E][\uDC00-\uDFFF])|(?:\uD80F[\uDC00-uDE07])

It's harder to read and operate with, and it's not that flexible, but still fits as workaround.