fileupload 验证

<asp:FileUpload ID="FileUpload1" runat="server" /><asp:RegularExpressionValidator   
id="FileUpLoadValidator" runat="server"   
ErrorMessage="图片格式不正确"   
ValidationExpression="^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))(.jpg|.JPG|.gif|.GIF)$"   
ControlToValidate="FileUpload1" Font-Size="Smaller"></asp:RegularExpressionValidator>