CODEWITHSUNDEEP
asp.netregex
Dave
Dave

Reputation: 13

RegularExpressionValidator - Validate first 2 characters

I am trying to validate a string entered into a textbox. I want to make sure that the first 2 characters are either 02, 04 or 09.

<asp:RegularExpressionValidator Display = "Dynamic" ControlToValidate = "check_number" ID="rxvValidCheckNumber1" ValidationExpression = "^(02|04|09)" runat="server" ErrorMessage="Valid Check Number required."></asp:RegularExpressionValidator>

If I enter a string that begins with 02, 04 or 09 the ErrorMessage still fires. What am I doing wrong?

Upvotes: 1

Views: 761

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626802

The ValidationExpression regex is anchored by default, and thus you need to match the entire input. You may match 0+ chars with .*:

ValidationExpression = "^(02|04|09).*"

To make it a bit more "elegant", you may use 0[249] after ^:

ValidationExpression = "^0[249].*"

The expression matches

  • ^ - start of string anchor
  • 0 - a 0 digit
  • [249] - a character class matching either 2 or 4 or9
  • .* - any 0+ chars other than line break chars.

If your textobx is multiline, you need to use (?s) singleline/dotall modifier

ValidationExpression = "(?s)^0[249].*"

or (to enable client side validation, the (?s) is not supported in JavaScript):

ValidationExpression = "^0[249][\s\S]*"

where [\s\S] matches any char including a line break char.

Upvotes: 2

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