Why do I get a FormatException when converting a string to a float?

Question

When I try to convert a string to float:

Console.WriteLine(float.Parse(\"6.59\"));

it throws an exception:

Unhandled Exc

Answer 1

I know everyone here has already given the reason for the problem experienced but perhaps somebody should just expand on why Invariant fixes it.

The CultureInfo class is used either directly or indirectly by classes that format, parse, or manipulate culture-specific data, such as String, DateTime, DateTimeOffset, and the numeric types to deal with the differences in the way different cultures write these types.

In case of the decimal type some cultures use a period(.) whilst others use a comma (,). By default when you are using the Conversion Libraries it will make use of your local culture (that is the country your OS to configured for).

By specifying Invariant you say that you expect thousand separators to be commas(,) and decimal deliminator to be a period(.) as it is in most cultures.

A big problem that sometimes happens is that these cultural conventions change from the OS point of view. For example the South African (ZA) culture info used to behave like the invariant culture. Microsoft changed this with Windows 8 where the decimal suddenly became a comma and the thousand separator a space.This resulted in many legacy systems written in .Net suddently breaking when one migrated them to newer operating systems.

In the end, deal normalize all local culture info to invariant and persist and deal with them in your business logic in this format. Then localize it back on the front end. Same goes for DateTime, as soon as possible convert to UTC, and only back when you render an output.