Removing hidden characters from within strings

Question

My problem:

I have a .NET application that sends out newsletters via email. When the newsletters are viewed in outlook, outlook displays a question mark in place

Answer 1

I used this quick and dirty oneliner to clean some input from LTR/RTL marks left over by the broken Windows 10 calculator app. It's probably a far cry from perfect but good enough for a quick fix:

string cleaned = new string(input.Where(c => !char.IsControl(c) && (char.IsLetterOrDigit(c) || char.IsPunctuation(c) || char.IsSeparator(c) || char.IsSymbol(c) || char.IsWhiteSpace(c))).ToArray());