Best way to validate currency input?

I have created the TextBox and CompareValidator below which I thought would allow input in the following forms:

• 5
• 5.00
• $5.00

Unfortunately it's not allowing the version with the dollar sign in it. What is the point of doing a type check against currency if you don't allow the dollar sign? Is there a way to allow this symbol?

            <asp:TextBox ID="tb_CostShare" runat="server" Text='<%# Eval("CostShare", "{0:$0.00}")%>' CausesValidation="true" />
            <asp开发者_如何学运维:CompareValidator   ID="vld_CostShare" 
                                    runat="server" 
                                    ControlToValidate="tb_CostShare" 
                                    Operator="DataTypeCheck" 
                                    Type="Currency" 
                                    ValidationGroup="vld" 
                                    ErrorMessage="You must enter a dollar amount for 'Cost Share'." />    

The CompareValidator doesn't support currency symbols. You can prefix your input control with the $ or use a regular expression validator, this page has an example.

The following pattern will match your examples (courtesy of http://www.regexlib.com):

^\$?([0-9]{1,3},([0-9]{3},)*[0-9]{3}|[0-9]+)(.[0-9][0-9])?$

Also, you could write a custom validator to parse the string, with or without $. But you would need to write some Javascript to get any client side validation.