Eto.Parse is a highly optimized recursive decent LL(k) parser framework that can be used to create parsers for complex grammars that go beyond the capability of regular expressions.
You can use BNF, EBNF, or Gold parser grammars to define your parser, code them directly using a fluent API, or use...
VBF.Compilers.Parsers is a GLR parser generator library. Compose grammars using Linq clauses, parsers with automatic error recovery can then be generated at runtime. Any context free grammar is supported, grammars with ambiguities can still be used by providing resolution rules.