Regular Expresion for FileUpdload

ID="FileToUpload"
runat="server"
ValidationGroup="Second"
Width="274px"
Font-Names="Verdana" />
*
ID="FileUploadValidator"
runat="server"
ControlToValidate="FileToUpload"
ErrorMessage="Upload PDF files only"
ValidationGroup="Second"
ValidationExpression="^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))(.jpg|.JPG)$"
Width="152px"
Font-Bold="True"
EnableViewState="False">

ID="RequiredFieldValidatorDocument"
runat="server"
ValidationGroup="Second"
ErrorMessage="Select a document to upload"
ControlToValidate="FileToUpload"
Font-Bold="True">

id="ButtonAddFile"
runat="server"
ValidationGroup="Second"
Height="23px"
Width="125px"
Text="Upload Document"
Font-Names="Verdana" />