Problem with Regex in .NET (C#)

Question

I'm trying to write a a regex to validate a string to match the following rules.

Must start with a-z (case insensitive)
Must only contain a-z A-Z 0-9 . -

I've put something together based on my limited knowledge and ran it through an online testing tool for a whole bunch of situations and the results were as I had hoped however when I place the pattern into my .NET code it doesn't match correctly.

The pattern I am using is,

[a-zA-Z][a-zA-Z0-9.\-]*

Is this the correct pattern or am I barking up the wrong tree?

Some examples of what I'm expecting.

craig.bovis - VALID
24craig - INVALID
craig@bovis - INVALID
craig24 - VALID
-craig24 - INVALID
craig24.bovis-test - VALID

Don't forget to start your RegEx with ^ to signify the start of the string. — Matt Hamilton
– Matt Hamilton, Commented May 5, 2010 at 11:55

Dean Harding · Accepted Answer · 2010-05-05 11:57:15Z

4

You're close. You need to anchor the match to the beginning and end of the string:

^[a-zA-Z][a-zA-Z0-9.\-]*$

The ^ mean "beginning of string" and $ means "end of string". Without them, the expression will match anywhere within the string as well.

answered May 5, 2010 at 11:57

Dean Harding

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