Error parsing regex pattern

Question

I'm writing a simple regex in c# to locate backslashes not preceded or followed by any backslashes:

Regex reg = new Regex(".*(?<!\\)\\(?!\\).*");

However, this statment generates an ArgumentException: "parsing ".(?" - Not enough )'s"

The group parentheses seem to match. Can anyone spot the problem?

Answer 1

use the string literal @

Regex reg = new Regex(@".*(?<!\\)\\(?!\\).*");

Answer 2

Put the @ symbol in front of your string, otherwise you need to double-escape the slashes (once for C#, and once for Regex).

Regex reg = new Regex(@".*(?<!\\)\\(?!\\).*");

or

Regex reg = new Regex(".*(?<!\\\\)\\\\(?!\\\\).*");