Question

This is, basically, a CultureInfo problem. Formally, in my country, the decimal separator is a comma (,) and a thousands separator is a dot (.). In practice, however, this is only used by accountants and diligent people. Normally people never use a thousands separator, and they use both a comma and a dot interchangeably as a decimal separator. I’ve seen this being the problem even in some Excel spreadsheets that I received from other people, with Excel not having recognized a dot as a decimal separator, leaving the field formatted as a string, rather than a number.

My “solution” thus far has been to simply replace all commas in user input with dots and then parsing the double with InvariantCulture, like so:

string userInput;
...
userInput = userInput.Replace(',', '.');
double result;
double.TryParse(userInput, NumberStyles.Float, CultureInfo.InvariantCulture, out result);

This will obviously fail when someone actually enters the thousands separator and this seems to me more like a hack than a real solution. So, other than making my own parser for doubles, are there any cleaner ways to handle this problem?

Answer 1

If you are using ASP.Net you can use the AjaxControlToolkit FilteredTextBox you can also accomplish the task using regular expressions and pattern matching. It is nearly always better to try and get a standard input than attempting to deal with every possible human input variable.

Some other links:
MaskedTextBox
WPF Tools FilteredTextBox