Formating a Phone Number

What am I doing wrong here? (Identifier expected)
<asp:Label ID="lblPrimaryPhone" runat="server" Text='<%# Eval("PrimaryPhone") != DBNull.Value ? (String.Format("{0:(###) ###-####}", Convert.ToInt64(Eval("PrimaryPhone")))) %>'></asp:Label>
I'm trying to format this as a US phone number. If I don't do it this way I get an error if the PrimaryPhone number is empty.