File Upload Validator always show error message

I add asp.net file upload control as follows:

<asp:FileUpload ID="filesFileUpload" runat="server" />
<asp:RegularExpressionValidator ID="RegularExpressionV开发者_JAVA技巧alidator3" runat="server" ErrorMessage="file types not supported"
ValidationExpression="\.(zip|rar|jpg|gif|png|eps|ai|psd|pdf)$" ControlToValidate="filesFileUpload"></asp:RegularExpressionValidator>

And always when I upload file that match the reg expression it show the error. How can I resolve this?

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Your regular expression checks for a single dot, followed by one of the extensions, all the way to the end of the string. You need to match the rest of the the filename (.+ matches one or more characters , ^ mean start of string):

ValidationExpression="^.+\.(zip|rar|jpg|gif|png|eps|ai|psd|pdf)$"

See this handy cheat sheet.