c# - RegularExpressionValidator always show error message -

here code of aspx:

<asp:fileupload id="imageupload" runat="server" style="margin-bottom: 5px" /> <br /> <asp:regularexpressionvalidator id="regularexpressionvalidator1" runat="server"   errormessage="only jpeg, png or gif files allowed!"  validationexpression="^(([a-za-z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))  +(.jpeg|.jpeg|.png|.png|.gif|.gif)$"   controltovalidate="imageupload"></asp:regularexpressionvalidator> 

i want filter jpeg, png , gif file in imageupload . , when upload jpeg,png , gif file , regularexpressionvalidator show error message .i want know what's wrong in code !

if want assert extension try this:

\.(jpeg|jpeg|png|png|gif|gif)$ 

this match ends in . followed either of above extensions.

edit:

without having tried , having no experience aspx, think should able use (?i:) make case insensitive:

(?i:\.jpeg|png|gif)$