Regular expression for price validation in asp.net c#

Regular expression for price validation in asp.net c#

          Need regular expression which have:

1.      Maximum 8 digits before decimal(.) point

2.      Maximum 4 digits after decimal point

3.      Decimal point is optional

Maximum valid decimal is 8 digits before decimal and 4 digits after decimal So 99999999.9999

<asp:TextBox ID="txtproductprice" runat="server"></asp:TextBox>

<asp:RegularExpressionValidator ID="reprice" ValidationExpression="^\d{0,8}(\.\d{1,4})?$" runat="server" ErrorMessage="Please Enter Your Correct Product Price" ControlToValidate="txtproductprice" Display="Dynamic" ForeColor="Red" SetFocusOnError="True"></asp:RegularExpressionValidator>