Question

Given the following RegEx expression, testing this on regexlib.com with the string ‘2rocks’ produces a ‘match’. However, in my .NET application, it’s causing the regex validator to throw a validation error.

^(?=.*[A-Za-z])[a-zA-Z0-9@\-_\+\.]{6,32}$ 

If I change the string to ‘rocks2’ in both my application and regexlib.com, I get a match in both places.

The goal is to have a regex expression, that requires the string to be between 6-32 chars in length, and allow A-Z, a-z, numeric and the other special characters included in the regex, forcing at least ONE letter.

Here’s the ASP mark up, I’m totally confused.

<asp:regularexpressionvalidator      id=vldRegEx_LoginID      runat='server'      ErrorMessage='Regex Error Message'      Display='Dynamic'      ControlToValidate='txtLoginID'      ValidationExpression='^(?=.*[A-Za-z])[a-zA-Z0-9@\-_\+\.]{6,32}$'>         <img src='images/error.gif' border='0'>  </asp:regularexpressionvalidator> 

Answer 1

The ValidationExpression you pass is actually the expression that is used as a client side javascript regex. Javascript regex doesn’t support all the features of .NET regex, which is why you’re running into issues. You have two options:

• Turn off client side validation and use server side validation only (set EnableClientScript=false on the validator)
• Rewrite the regex to be a valid javascript regex (javascript regex tester: http://regexpal.com/)