Try it:
^\$\d+(,\d+)+$
Some random coincidences;
$1622,40,749 $37,5844
Regex r = new Regex(@"^\$\d+(,\d+)+$"); string[] partNumbers = { "$567,76", "$567,76,87", "$567,76,87," }; foreach (var i in partNumbers) { Console.WriteLine("{0} {1} a valid part number.", i, r.IsMatch(i) ? "is" : "is not"); }
$567,76 is a valid part number. $567,76,87 is a valid part number. $567,76,87, is not a valid part number.
Here is the DEMO .
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