How can block textchanged (stop postback), if validation is failed

Question

I have a textbox, which has RegularExpressionValidation connected with it, and also has ontextchanged function autopostback is true.

Now the case is if RegularExpressionValidation failed, it will show error text in 1 second and disappeared, then do the ontextchanged function.

How can block textchanged, if validation is failed?

Answer 1

I figure my RegularExpression has some error, after I fixed it, it is solved.