Develop Reference

Changing DateSeparator doesn't work for all CultureInfos

I am trying to change the DateSeparator and it doesn't work for all cultures. Below, I'm trying to format a date in the Japanese and Korean Cultures and use an underscore for the date separator. It works as expected for Japan, but not for Korea. I've found some other cultures that behave this way as well.
CultureInfo jpCulture = CultureInfo.CreateSpecificCulture("jp");
DateTimeFormatInfo jpFormat = jpCulture.DateTimeFormat;
jpFormat.DateSeparator = "_";
CultureInfo koCulture = CultureInfo.CreateSpecificCulture("ko");
DateTimeFormatInfo koFormat = koCulture.DateTimeFormat;
koFormat.DateSeparator = "_";
string jpDate = DateTime.Now.ToString("d", jpFormat);
string koDate = DateTime.Now.ToString("d", koFormat);
System.Console.WriteLine($"My local (US) formatting: {DateTime.Now:d} - JP Formatter: {jpDate} - KO Formatter: {koDate}");
Will output:
My local (US) formatting: 8/3/2020 - JP Formatter: 08_03_2020 - KO Formatter: 2020-08-03
I had expected the Korean formatted string to use underscores as well.
My goal is to always have a Date format that's appropriate for the culture (YMD, or MDY or DMY) but using a customizable separator. Is there a more appropriate way to do that?

This happens because the d standard date/time format specifier uses the DateTimeFormat.ShortDatePattern to produce the output string. Only a "/" character in the pattern will be replaced by the locale's DateSeparator.
If you add the following to your test application:
Console.WriteLine(koCulture.DateTimeFormat.ShortDatePattern);
Console.WriteLine(jpCulture.DateTimeFormat.ShortDatePattern);
you will see the following output:
yyyy-MM-dd
MM/dd/yyyy
The Japanese string contains the "/" character that will be replaced by DateTimeFormat.DateSeparator, so that works.
The Korean one, however, uses - - which won't be replaced!
A possible workaround is to change the Korean short date format like so:
koCulture.DateTimeFormat.ShortDatePattern = koCulture.DateTimeFormat.ShortDatePattern.Replace('-', '/');
(although that feels a bit flaky to me...)
As to why the Korean short date pattern is set up like this, I have no idea. It seems like a bug, but only Microsoft could answer that!
It looks like loads of the cultures have "incorrect" ShortDatePattern values where Microsoft has put in the actual date separator character rather than a "/" character, as the following code shows:
foreach (var culture in CultureInfo.GetCultures(CultureTypes.AllCultures))
{
var dtf = culture.DateTimeFormat;
if (dtf.DateSeparator != "/" && dtf.ShortDatePattern.Contains(dtf.DateSeparator))
Console.WriteLine(culture.EnglishName + " has incorrect short date pattern: " + dtf.ShortDatePattern);
}

There is a problem with DateSeparator, only / is replaced with specified separator, this can be seen in source.
For any culture with ShortDatePattern containing other separator than / the DateSeparator is not working.

Convert date from dd-mm-yyyy to mm/dd/yyyy

I need to convert the date format from dd-mm-yyyy to mm/dd/yyyy. I tried below one, but it is converting the format to mm-dd-yyyy.
packDate = packDateControl.SelectedDate.Value.ToString("MM/dd/yyyy");
I need it to be like this mm/dd/yyyy. How to do this in c#.
Thanks

When used in a custom date format string, the / character substitutes the locale specific date separator, so for English locales, this tends to be /, but for Turkey, it would be .
So, there are a number of options, you could either quote them as text, so something like:
packDate = packDateControl.SelectedDate.Value.ToString("MM'/'dd'/'yyyy");
Or you could specify the locale to use:
var culture = new CultureInfo("en-US");
packDate = packDateControl.SelectedDate.Value.ToString("MM/dd/yyyy", culture);
Or you could use a standard format string, with the relevant locale:
var culture = new CultureInfo("en-US");
packDate = packDateControl.SelectedDate.Value.ToString("d", culture);
For more information on custom date format strings, check out MSDN

Not sure what control you are using, but try . . .
packDate = packDateControl.SelectedDate.Date.ToString("MM/dd/yyyy");
Swapping .Value for .Date.

Is a DateTime.ToString format expression affected by the current culture locale?

I have some code that is logging a timestamp in format from a thick client app
DateTime.UtcNow.ToString("MM/dd/yy HH:mm:ss")
Now, on a client running in China (not sure exactly which locale) this is producing a date in the log with the format
11-20-13 02:14:03
I notice it's using - instead of / to delimit the parts, even though I explicitly wanted /
I tried to set the current culture to Chinese simplified zh-CN but I wasn't able to reproduce how the remote client was able to produce that string
Does current culture locale affect the output of this format string? Or does / have some other meaning I'm not aware of?

Yes, the / character is a placeholder for whatever the current culture uses to separate parts of the date. From MSDN:
The "/" custom format specifier represents the date separator, which is used to differentiate years, months, and days. The appropriate localized date separator is retrieved from the DateTimeFormatInfo.DateSeparator property of the current or specified culture.
As with other format specifiers, you can escape the / with a \:
DateTime.UtcNow.ToString(#"MM\/dd\/yy HH\:mm\:ss")
Or specify an explicit culture when formatting the string:
DateTime.UtcNow.ToString("MM/dd/yy HH:mm:ss", CultureInfo.InvariantCulture)

Yes, that's how it works. / is being replaced with the local date separator. The same applies to : as a time separator. You can find more on MSDN: Custom Date and Time Format Strings.
To change that, escape them with \:
DateTime.UtcNow.ToString(#"MM\/dd\/yy HH\:mm\:ss")

Convert object to single. CultureInfo problems

So I have the following line of code :
Single xFreq = Convert.ToSingle(param, CultureInfo.InvariantCulture);
Variable param is a System.Object Any reason the result is not the same if the "," separator is used instead of the "."? For example 0.45 is converted correctly but 0,45 is converted to 45... This thing keeps bugging me for the last hour...

Not sure what your question is since you explicitly specifying InvariantCulture for parsing the string value - hence "." is used as separator.
You need to specify CultureInfo that matches your input. Generally to parse user input you need to use current culture. If input comes from some other source you have to know what culture it was serialized with.

Because the decimal separator is Culture dependent, as other posts clarified, for InvariantCulture it's "." (CultureInfo.InvariantCulture.NumberFormat). You can look at the NumberFormatInfo article for more details regarding other separators for number types.

Invariant culture converts from and to "." like a separator. Instead the string you converting from is not in in ariant culture format, hou need specify string's culture.
Thd basic technique in this case could be to STORE in invariant culture, but show to user what he wants like a separator, so you will get rid of any culture dependent problem and user will happy to see what he likes to see.
Regards.

C# parsing float from string

I'm reading numbers from XML files. Other numbers are with a comma separator (0,1111) and others with dot (0.1111). How do I parse these numbers so I get the desired result in the end? I tried using float.Parse(reader.Value, System.Globalization.CultureInfo.InvariantCulture); but it doesn't work. For example I have reader.Value = "0,01119703" and is parsed as 1119703.0.

I don't believe that it is possible to work with two different decimal separators at the same time. I think I would just use Replace() to change any commas into dots.
float.Parse(reader.Value.Replace(',', '.'), System.Globalization.CultureInfo.InvariantCulture);

Not sure this is the greatest solution, but perhaps you could rely on a set of known "Custom" number formats. For instance, you could declare two custom number formats (either from scratch or based off of a known format) such as:
private static readonly NumberFormatInfo DecimalSeparatorFormat = new NumberFormatInfo { NumberDecimalSeparator = ".", NumberGroupSeparator = "," };
private static readonly NumberFormatInfo CommaSeparatorFormat = new NumberFormatInfo { NumberDecimalSeparator = ",", NumberGroupSeparator = "." };
And then try parsing the number through your known accepted formats:
if (!Single.TryParse(unparsedValue, NumberStyles.Float, DecimalSeparatorFormat, out parsedValue) && !Single.TryParse(unparsedValue, NumberStyles.Float, CommaSeparatorFormat, out parsedValue))
throw new FormatException("Number format not supported");
This assumes that you have a finite number of known formats, if your inputs can truly be in any culture, then you may be out of luck with finding a great solution.
The one win with this approach is you are at least being explicit in the formats you are able to support rather than relying on a simple string replace (which may result in an invalid format).

Is there anything in the XML files that will tell you which format is being used? There's not a built-in way in .NET to have two different allowed decimal separators. If there's nothing telling you which format a number is going to be in, then you could always check to see whether the string contains a period or a comma, and create a NumberFormatInfo with that as the decimal separator. Of course, this won't work if any of the numbers have a period or comma as a thousands separator.