Language invariant Double.ToString()

Question

I am passing a double across a network, currently I do

double value = 0.25;
string networkMsg = "command " + value;

the networkMsg is fine in english where its 0.25 and french where its 0,25, but when i go from a french computer to an english computer one side is making it 0.25 and the other is trying to read 0,25.

So i can to use region invariant methods in my code.

I have found Val(networkMsg) that will always read 0.25 no matter the region.

but I cannot find a guaranteed way of converting from value to 0.25 region invariant. would value.toString("0.0") work?

Answer 1

Use:

string networkMsg = "command " + value.ToString(CultureInfo.InvariantCulture);

or:

string networkMsg = string.Format(CultureInfo.InvariantCulture, "command {0}", value);

This needs using System.Globalization; in the top of your file.

Note: If you need full precision, so that you can restore the exact double again, use the Format solution with the roundtrip format {0:R}, instead of just {0}. You can use other format strings, for example {0:N4} will insert thousands separators and round to four dicimals (four digits after the decimal point).

---

Since C# 6.0 (2015), you can now use:

string networkMsg = FormattableString.Invariant($"command {value}");

Answer 2

The . in the format specifier "0.0" doesn't actually mean "dot" - it means "decimal separator" - which is , in France and several other European cultures. You probably want:

value.ToString(CultureInfo.InvariantCulture)

or

value.ToString("0.0", CultureInfo.InvariantCulture)

For info, you can see this (and many other things) by inspecting the fr culture:

var decimalSeparator = CultureInfo.GetCultureInfo("fr")
            .NumberFormat.NumberDecimalSeparator;