showing all error messages

Hi ,

I'm developing an application(during a training course) and I have provided appropriate error message for each field in a form.Fields are required and have character limits.

however if we leave fields empty ,we will face as follows:

http://uupload.ir/files/qv6b_asp_error_message.png

But it also has length constraint for example :

http://uupload.ir/files/nj_asp_error_message_2.png

and after that if the user says  "It  could be told at that stage too" he or she is absolutely right.
How to make the app render all error messages?