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Editorial Team
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Asked: 2026-05-14T18:45:21+00:00

I’m trying to write a a regex to validate a string to match the

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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
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1 Answer

  1. Editorial Team

    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.

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