Question

I’m trying to implement a numeric converter that takes an object and converts it to the required type.

I found a problem though: when I test “1,5” with the “en-US” culture Convert.ToSingle and Convert.Double simply returns “15” instead of throwing an exception that it cannot convert this value, which I would actually expect because “1,5” is invalid.

Does anyone know why?

Answer 1

No, "1,5" is perfectly valid. Similar to how "1,500" parses to 1500. Basically, the group separators (, in en-US) are simply ignored when parsing.

If you don’t want it to do this, specify the NumberStyles:

int i = int.Parse("1,5", NumberStyles.Integer);

note that this is a [Flags] enum, and importantly I’m not including AllowThousands. Another approach could be:

int i = int.Parse("1,5", NumberStyles.Any & ~ NumberStyles.AllowThousands);

which allows everything except group separators. Of course, "1,500" will now fail.