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.

To pass specific Date format

How we can pass specific Date format like "MM/dd/YYYY" in place of System.DateTime in below code.
new ObjectParameter("FromDate", typeof(System.DateTime));

I'm not sure but i guess you are looking for a way to convert the DateTime to string in this format. Then you can use DateTime.ToString with an appropriate format string:
string result = DateTime.Now.ToString("MM/dd/yyyy", System.Globalization.DateTimeFormatInfo.InvariantInfo);
I'm using InvariantInfo to force the / as separator. Otherwise it would be replaced with your localized date separator. See: The "/" Custom Format Specifier.
Another way to force / as date separator is to escape the / format specifier with ':
string result = DateTime.Now.ToString("MM'/'dd'/'yyyy");

You can't.
A DateTime does not have any implicit format. It just have date and time values. Format concept only applies when you get it's textual (string) representation.
There is only two constructor of that ObjectParameter which one is expect Object and the other one expect Type as a second parameter.

You can specify how you want the DateTime formatted when using .ToString(), by entering a parameter in the ToString() method, like so: somedatetime.ToString("d");
You can read more about the formatting here: DateTime.ToString Method at MSDN

Parse DateTime in C#

I am trying to parse a TimeString that looks like:
11/Apr/2014:00:00:12 +0200
my code looks like
DateTime.ParseExact("11/Apr/2014:00:00:12 +0200", "dd/MMM/yyyy:HH:mm:ss zzz", null)
I looked at the MSDN and it looks good for me but I have no clue why I always get a FormatException.

You should add the InvariantCulture as a format provider.
var d = DateTime.ParseExact("11/Apr/2014:00:00:12 +0200", "dd/MMM/yyyy:HH:mm:ss zzz", CultureInfo.InvariantCulture);
Your format string is considering that the / and : characters are specific format separators that will resolve to the ones defined in your current culture, just as HH would signify "hours" in your format. Please refer to this page to see that the time separator and date separator are predefined and will be replaced by the culture specific values.
It is possible to escape the special characters but I think that in the long run your code will be much safer with the InvariantCulture

Parse Datetime string

I'm trying to convert the following string to datetime. I've searched high and low and can't find the exact formats string and I don't want to resort to parsing it manually.
var dateString = "20110828T134108+0100";
All my attempts fail with FormatException.

Have you tried this?
var date = DateTime.ParseExact( dateString
,"yyyyMMdd\THHmmsszzz"
,CultureInfo.InvariantCulture
);
From MSDN:
If format is a custom format pattern that does not include date or
time separators (such as "yyyyMMdd HHmm"), use the invariant culture
for the provider parameter and the widest form of each custom format
specifier. For example, if you want to specify hours in the format
pattern, specify the wider form, "HH", instead of the narrower form,
"H".

The documentation on the format string is here: http://msdn.microsoft.com/en-us/library/8kb3ddd4.aspx
That should get you started. :)

try this format: "yyyyMMdd'T'HHmmss"

Have you tried this:
DateTime.ParseExact("20110828T134108+0100", "yyyyMMdd'T'HHmmsszzzz", CultureInfo.InvariantCulture);

Formatting numbers in different cultures

Assuming an invariant culture, is it possible to define a different group separator in the format - than the comma?
Thread.CurrentThread.CurrentCulture = CultureInfo.InvariantCulture;
Console.WriteLine(String.Format("{0:#,##0}", 2295));
Output:
2,295
Desired output:
2.295
The invariant culture is a requirement because currencies from many different locales are being formatted with format strings, that have been user defined. Ie for Denmark they have defined the price format to be "{0:0},-", while for Ireland it might be "€{0:#,##0}".

When you have different format strings, this does not mean that you have to use InvariantCulture. If you have a format string for germany e.g. you format this string using the Culture("de-de"):
String.Format(CultureInfo.GetCultureInfo( "de-de" ), "{0:0},-", 2295) //will result in 2.295,-
String.Format(CultureInfo.GetCultureInfo( "en-us" ), "{0:0},-", 2295) //will result in 2,295,-
Alternatively you can specify your custom number format info:
NumberFormatInfo nfi = new NumberFormatInfo( )
{
CurrencyGroupSeparator = ":"
};
String.Format(nfi, "{0:0},-", 2295) //will result in 2:295,-

The normal approach would be to not use an Invariant culture.
You do specify the formatting in Invariant style, but the proper symbols would be substituted, #,##0.00 will come out as 1.234,50 or as 1,235.50 depending on the actual culture used.