>Do you know how this VFP format
>
>

>transform(extension, '$,$$$,$$9.99')

>
>translates into StringBuilder AppendFormat ?

Not sure if this is related or if that could help, but to format dollar value in .NET, I use this:

        ' Format a value for a dollar
        ' expN1 Value
        ' expC1 Separator
        Public Function GetFormatValueDollar(ByVal tnValue As Double, ByVal tcSeparator As String) As String
            Dim lcValue As String = ""
            Dim loCultureInfo As CultureInfo = Nothing

            ' Based on the language
            Select Case nLanguage

                ' English
                Case 1
                    loCultureInfo = oApp.oCultureInfoEnglish

                    ' French
                Case 2
                    loCultureInfo = oApp.oCultureInfoFrench

                    ' Spanish
                Case 3
                    loCultureInfo = oApp.oCultureInfoSpanish

                    ' Portuguese
                Case 4
                    loCultureInfo = oApp.oCultureInfoPortuguese

            End Select

            loCultureInfo.NumberFormat.CurrencyDecimalSeparator = "."
            loCultureInfo.NumberFormat.CurrencyGroupSeparator = tcSeparator

            ' If we format the dollar sign as per the language
            If oApp.lFormatDollarAsPerTheLanguage Then

                ' Based on the language
                Select Case nLanguage

                    ' English
                    Case 1

                        ' French
                    Case 2
                        loCultureInfo.NumberFormat.CurrencyPositivePattern = 1

                        ' Spanish
                    Case 3

                        ' Portuguese
                    Case 4

                End Select

            End If

            lcValue = tnValue.ToString("C", loCultureInfo)

            Return lcValue
        End Function