Regex for word.otherword

Question

I want a Regular Expression for a word.otherword form. I tried \b[a-z]\.[a-z]\b, but it gives me an error at the \. part, saying Unrecognized escape sequence. Any idea what's wrong? I'm working under .NET C#. Thanks!

LE:

john.Smith or JoHn.SmItH or JOHN.SMITH should work.

John Smith or john!Smith or john.Smith.Smith shouldn't work.

Answer 1

Try this :

foundMatch = Regex.IsMatch(SubjectString, @"\b[a-z]\.[a-z]\b");

Probably you were not using @?

Your regex tries to match a.a this means a single character. But since you want it to match complete words you need a quantifier e.g.

\b[a-z]+\.[a-z]+\b

Finally you may want to use the case insensitive match to allow for words with capital letters to be matched too :

foundMatch = Regex.IsMatch(SubjectString, @"\b[a-z]+\.[a-z]+\b", RegexOptions.IgnoreCase);

This will match all words.words with at least one character for each word regardless of capitalization.

This will match all word.otherword only if there is a space behind the first word or it is the start of the string and only if there is a space after the second word or it is the end of the string.

foundMatch = Regex.IsMatch(SubjectString, @"(?<=\s|^)\b[a-z]+\.[a-z]+\b(?=\s|$)", RegexOptions.IgnoreCase);

Answer 2

Try this regex for word.word format:

@"\b([a-z]+)\.\1"

For word.otherword use this:

@"\b[a-z]+\.[a-z]+\b"