Question

I use Asp.net and C#.

I need force the User to add in a TextBox Control only between 4 and 128 characters text.

I would like to use a ValidationExpression Property for a Validation Control.

Could you point me out a correct Regular Expression?

Notes: I’m using this code right now, but it seems not working properly if there are double spaces or break line in the TextBox

ValidationExpression="^.{4,128}$"

Thanks for your time on this!

Answer 1

Your expression is correct. Just use the Singleline modifier, to make the dot also match newline characters.

RegexOptions.Singleline

Or as inline modifier

"^(?s)(.){4,128}$"

RegexOptions Enumeration
Regular Expression Options