C# replace string except when preceded by another

Question

I want to replace all ocurrence of " by \" in a string except if this " is preceded by a \ for exemple the string hello "World\" will become hello \"World\"

Is it possible without using regex ? But if I have to use regex, what kind have I to use ?

Thanks for help, regards,

Answer 1

You could use a lookbehind:

var output = Regex.Replace(input, @"(?<!\\)""", @"\""")

Or you could just make the preceeding character optional, for example:

var output = Regex.Replace(input, @"\\?""", @"\""")

This works because " is replaced with \" (which is what you wanted), and \" is replaced with \", so no change.