Lex and Yacc are useful tools that you would use if you want to create a compiler, a transpiler or you just want to interpret a formal language.
YaccLexTools is focused on C#. Other tools are available for other programming languages like C/C++, F#, Java, etc.
YaccLexTools translantes Yacc and Lex files in C# code thanks to the tools GPPG and GPLEX and simplify the use of these tools in the C# projects building process.
Read my blog post for more details:
https://devnotes.ernstc.net/yacclextools
Nuget package: https://www.nuget.org/packages/YaccLexTools/