此正则表达式模式的C＃等效项

Question

I have this regular expression pattern: .{2}\\@.{2}\\K|\\..*(*SKIP)(?!)|.(?=.*\\.)

It works perfectly to convert to replace the matches to get

trabc@abtrec.com.lo => ***bc@ab*****.com.lo

demomail@demodomain.com => ******il@de*********.com

But when I try to use it on C# the \\K and the (*SKIP) and (*F) are not allowed.

what will be the c# version of this pattern? or do you know a simpler way to mask the email without the unsupported pattern entries?

Demo

UPDATE:

(*SKIP): this verb causes the match to fail at the current starting position in the subject if the rest of the pattern does not match

(*F): Forces a matching failure at the given position in the pattern (the same as (?!)

Answer 1

Try this regex:

\w(?=.{2,}@)|(?<=@[^\.]{2,})\w

Click for Demo

Explanation:

• \\w - matches a word character
• (?=.{2,}@) - positive lookahead to find the position immediately followed by 2+ occurrences of any character followed by @
• | - OR
• (?<=@[^\\.]{2,}) - positive lookbehind to find the position immediately preceded by @ followed by 2+ occurrences of any character that is not a .
• \\w - matches a word character.

Replace each match with a *

Answer 2

You can achieve the same result with a regex that matches items in one block, and applying a custom match evaluator:

var res = Regex.Replace(
    s
,   @"^.*(?=.{2}\@.{2})|(?<=.{2}\@.{2}).*(?=.com.*$)"
,   match => new string('*', match.ToString().Length)
);

The regex has two parts:

• The one on the left ^.*(?=.{2}\\@.{2}) matches the user name portion except the last two characters
• The one on the right (?<=.{2}\\@.{2}).*(?=.com.*$) matches the suffix of the domain up to the ".com..." ending.

Demo.