views:

2033

answers:

9

I have the following number: 4.3

I'd like to display this number as 4,3 for some of our European friends.

I was under the impression that the following line would do the trick:

string ret = string.Format("{0:0,0}", 4.3); // returns "04", not "4,3"

Am I using the incorrect string?

+2  A: 

The number formatting by default uses the NumberFormatInfo from the current CultureInfo, so that it displays using the regional settings on the computer.

Therefore, you don't really need to do anything special about it, except maybe making sure that the correct CultureInfo is being used.

As for the question, yes the string is invalid. A "," denotes a thousand-separator, not the decimal-separator. Have a look the the NumberFormatInfo and the custom number formats.

Lucero
+2  A: 

For a more general solution, you can set the thread's UI culture to the culture used by your European friends. This will affect the presentation of numbers, currency, dates, etc.

bzlm
+5  A: 

I think:

string.Format(System.Globalization.CultureInfo.GetCultureInfo("de-DE"), "{0:0.0}", 4.3);

should do what you want.

JDunkerley
will take care of dealing with thousands as well, which are done different as well.
dove
But it has the disadvantage that you have to manually insert the culture information in EVERY ToString, String.Format, Number.Parse and similar method in your code.
Foxfire
+1  A: 

Use a CultureInfo that has commas instead of decimal point (French for instance) :

string.Format(CultureInfo.GetCultureInfo("fr-FR"), "{0:0.0}", 4.3);
Thomas Levesque
+3  A: 
NumberFormatInfo nfi = new NumberFormatInfo();
nfi.NumberDecimalSeparator = ",";
nfi.NumberGroupSeparator = ".";

double num = 4.3;
string ret = num.ToString(nfi);    // 4,3
LukeH
+1 nice solution, does exactly what it says on the tin.
James
@James: except that it's pretty useless since culture support is built into .NET. Better to do this the supported way rather than reinventing it.
Mats Fredriksson
@Mats: And what happens if you decide to pick an arbitrary European `CultureInfo` object (for example, "de-DE" or "fr-FR") and that culture has been customised to use a different decimal separator? I know it's an unlikely scenario but it could happen. Using my code you will always get a `,` as the decimal separator, regardless of any customisations.
LukeH
But you don't want to get a `,` always, you want to format strings according to user's regional settings (including his/her customized settings).
Groo
@Groo: That's not what the question says. It specifically states "display this number as 4,3" **not** "display this number according to user's regional settings (including his/her customized settings)".
LukeH
@luke: it says "display this number as 4,3 for some of our European friends" which I would interpret as "display values according to the end users locale", but I might be wrong. If he want to display it according to the end users culture I would use the culture. Not a randomly picked one, true, but the end users.
Mats Fredriksson
+6  A: 

This depends on what you want to do. If you want to make your entire application ready for some other language output just use

System.Threading.Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo ("de-DE");

If you want to have a mixed language application (that means some of the outputs are formatted in one language some in another) you have to use the overloads of the specific String functions like:

var culture =  System.Globalization.CultureInfo.GetCultureInfo("de-DE");   
String.Format (culture, "{0:0.0}", 4.3);

The first method is preferred if it is possible because you only need one single line in your application and everything will be as expected. In the second you have to add the culture parameter to every String ouput method in your entire application.

Foxfire
That's a great answer. Do you know if this is settable via a config file?
Greg
A: 

Yes, you are using the wrong string, and also the problem can't be solved by only providing a formatting string.

What your formatting string does is to format the number using the pattern "0", then aligned to the length 0.

When you specify the decimal separator in a formatting string it's always a period regardless of the current culture. The decimal separator in the result of the formatting on the other hand is always the one used by the current culture. So, to get a comma as decimal separator in the result you have to make sure that the culture used for the formatting is one that uses comma as decimal separator.

You can either set the current culture for the thread so that it's used by default by the formatting, or specify a culture in the call:

string ret = String.Format(CultureInfo..GetCultureInfo(1053), "{0:0.0}", 4.3);
Guffa
+1  A: 

Settings the thread culture will do this conversion automatically. However, if you want to format this with a custom string you can do the following:

string ret = string.Format("{0:0.00}", 4.3);

or

string ret = (4.3f).ToString("0.00");

The "." is the format specifier for decimal point for the current culture. More info for custom number formats are found at: http://msdn.microsoft.com/en-us/library/0c899ak8.aspx

You can always check what character for the decimal point is with:

string decimalChar = Thread.CurrentThread.CurrentCulture.NumberFormat.CurrencyDecimalSeparator;
Torbjörn Hansson
A: 

Number formatting can be handled for you by the framework if you use the correct culture when manipulating the number.

Console.WriteLine(4.3);

Console.WriteLine(4.3.ToString(CultureInfo.GetCultureInfo("fr-fr")));

Thread.CurrentThread.CurrentCulture = CultureInfo.GetCultureInfo("fr-fr");
Console.WriteLine(4.3);

If you want to do a "one-off" display, the second approach will work. If you want to display every number correctly, you really should be setting the current thread's culture. That way, any number manipulation will handle decimal separators, grouping characters and any other culture-specific things correctly.

The same goes for parsing numbers. If a user enters 1,234, how do you know whether they have entered 1.234 (the comma being the decimal separator) or 1234 (the comma being a grouping separator)? This is where the culture helps out as it knows how to display numbers and can also be used to parse them correctly:

Console.WriteLine(double.Parse("1,234"));

Console.WriteLine(double.Parse("1,234", CultureInfo.GetCultureInfo("fr-fr")));

Thread.CurrentThread.CurrentCulture = CultureInfo.GetCultureInfo("fr-fr");
Console.WriteLine(double.Parse("1,234"));

The above will output 1234 (the comma is a decimal separator in my en-us default culture), 1.234 (the comma is a decimal separator in French) and 1,234 (again, the comma is a decimal separator in French, and also the thread's culture is set To French so it displays using this culture - hence the comma as a decimal separator in the output).

adrianbanks