Does RegularExpressionValidator use other flavor than Regex?

Question

I want to do preliminary check if entered string looks like Vehicle Identification Number (VIN). I know what it consists of 17 letters and digits, but letters I, O and Q are

Answer 1

The RegularExpressionValidator also supports client-side validation using JavaScript, where the JavaScript Regex engine is used. The difference you see is the difference between the JavaScript and the .NET regex implementation. You can disable client-side validation and thus force the validator to use the .NET regex engine, at the price of the additional post-back.