javascript - Unable to use server side delimiters inside title property -

the title in below expression comes string instead of evaluated expression.

<my:modal id="dialog_prepopchat" runat="server" modaltype="dialog" background="none" title='<% messagehelper.getmessagetext(283121) %>' /> 

the title shows - '<% messagehelper.getmessagetext(283121) %>' instead of - 'live help'

what doing wrong?