<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>&nbsp;
        <asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" ControlToValidate="TextBox1"
            Display="Dynamic" ErrorMessage="*" ValidationExpression="^(-?[0-9]*[.]*[0-9]*)$"></asp:RegularExpressionValidator>&nbsp;
        <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="TextBox1"
            ErrorMessage="*"></asp:RequiredFieldValidator>