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Format DateTime object from System time format to required format

My system time is of the format dd-MMM-yy (02-Dec-16). The format I want to convert it to is "yyyy/MM/dd". I've basically been playing around with all the other datetime formats that my system offers and this is the parsing statement I've figured out that works for All of them (except this) -
CultureInfo provider = CultureInfo.InvariantCulture;
string date_format = "yyyy/MM/dd HH:mm:ss tt";
DateTime now_value = DateTime.ParseExact(DateTime.Now.ToString(date_format), date_format, provider);
return now_value.ToString(date_format);
But this doesn't work for the aforementioned dd-MMM-yy format. Can someone please tell me what I am doing wrong here?
(Sidebar -Is there a more efficient way in which I can write this above snippet?)

You don't need to convert DateTime to string and then convert back to DateTime and again back to string, if you have DateTime input just call the ToString with the format as below
string dt =DateTime.Now.ToString("yyyy/MMM/dd", CultureInfo.InvariantCulture);
for your example :
DateTime now_value = DateTime.ParseExact("02-Dec-16", "dd-MMM-yy", System.Globalization.CultureInfo.InvariantCulture);
return now_value.ToString("yyyy/MM/dd");

Try This:
string date_format = "yyyy-MMM-dd";
string date_now = DateTime.Now.ToString(date_format,CultureInfo.CreateSpecificCulture("en-US"));
return date_now;
Even This should also work:
string date_format = "yyyy-MMM-dd";
string date_now = DateTime.Now.ToString(date_format);
return date_now;

I think best way would be to create an extension method for multiple date formats,
var inputDate = "02-Dec-2016";
string[] availaible_input_date_format = { "dd-MMM-yyyy", "dd/MMM/yyyy" }; // add as many formats availible
var date_format = "yyyy/MMM/dd";
DateTime outputDate;
DateTime.TryParseExact(inputDate, availaible_input_date_format, null, DateTimeStyles.None, out outputDate);
Console.WriteLine(outputDate.ToString(date_format));

You can try this:
datetime yourdatetime = new datetime();
string converteddatetime = yourdatetime.toString("yyyy/MM/dd");

Reading date from string format

I have to read a date in this format in c#
yyyy/MM/dd HH:mm:ss
I cannot change the format because is written by another application
The date is a string like
2009/11/17 12.31.35
How i can read this format without parsing it(without split if possible)
thanks

I cannot change the format because is written by another application
Solution 1: You don't need to change the format for reading it.
Try This:
DateTime dt;
DateTime.TryParseExact(date, "yyyy/MM/dd HH.mm.ss",
CultureInfo.InvariantCulture, DateTimeStyles.None, out dt);
OR
How i can read this format without parsing it(without split if
possible)
Solution 2: If you want to extract the values from the date string.
Try This:
string str = "2009/11/17 12.31.35";
string year = str.Substring(0, 4); //2009
string month = str.Substring(5, 2); //11
string date = str.Substring(8, 2); //17
string Hours = str.Substring(11, 2); //12
string minutes = str.Substring(14, 2);//31
string seconds = str.Substring(17, 2);//35

Use DateTime.ParseExact, where you can supply your custom date format

Try replacing . with : an then ParseExtract
string dt= "2009/11/17 12.31.35";
var dt2= ss.Replace('.', ':');
DateTime d = DateTime.ParseExact(dt2, "yyyy/MM/dd HH:mm:ss", CultureInfo.InvariantCulture);
or just
DateTime d = DateTime.ParseExact("2009/11/17 12.31.35", "yyyy/MM/dd HH.mm.ss", CultureInfo.InvariantCulture);

Converting a date string in C#

I have a date string with the format "dd.MM.yyyy" (eg. "01.02.2004") and want to convert it to "yyyy-MM-dd" with String.Format(...) or DateTime.ParseExact(...) or whatelse.
Actually I only get exceptions. So the usage of the following code doesn't work:
String dateString = "01.02.2004";
datestring = String.Format("{yyyy-MM-dd}", dateString);
What is wrong with that? Is there an alternative with DateTime.ParseExact(..)?

You need to parse it into a DateTime, then call ToString() with a different format:
DateTime date = DateTime.ParseExact(dateString, "dd.MM.yyyy", CultureInfo.InvariantCulture);
date.ToString("yyyy-MM-dd")

You need to create a Datetime object first.
try something like:
DateTime t = DateTime.parse("01.02.2004");
String result = t.ToString("{yyyy-MM-dd}", CultureInfo.InvariantCulture);

You have to convert it to a DateTime first with an appropriate CultureInfo:
String dateString = "01.02.2004";
var deCulture = System.Globalization.CultureInfo.CreateSpecificCulture("de-DE");
DateTime dt = DateTime.Parse(dateString, deCulture);
dateString = dt.ToString("yyyy-MM-dd");
Demo

String dateString = "01.02.2004";
dateString = DateTime.ParseExact(dateString, "dd.MM.yyyy", CultureInfo.InvariantCulture)
.ToString("yyyy-MM-dd");
What's wrong with your attempt is:
When using a format string, the items need to be listed in a format like {0:yyyy-MM-dd}. The 0: is necessary.
When you're using string.Format(), the variable is a string, so the format string yyyy-MM-dd has no meaning there.

You're parsing a string as argument to String.Format? What do you expect out of it?
You should do something like this:
try
{
var date = DateTme.ParseExact("yyyy.MM.dd", dateString, CultureInfo.InvariantCulture);
var result = date.ToString("yyyy-MM-dd");
}
catch(Exception e) { /* ... */}

DateTime.Parse with a custom DateTimeFormatInfo throws an exception

Why is this code throwing an exception?
var dateTime = "2012-03-21_15.12";
var format = new DateTimeFormatInfo()
{
FullDateTimePattern = "yyyy-MM-dd-HH_mm.ss"
};
// FormatException: String was not recognized as a valid DateTime.
var parse = DateTime.Parse(dateTime, format);

Your format string and the date string do not match.
You seem to have forgotten either the hours or minutes portion in the date string.
This:
var dateTime = "2012-03-21_15.12";
Should probably look like:
var dateTime = "2012-03-21-15_54.12";
And I suggest using DateTime.ParseExact:
DateTime.ParseExact("2012-03-21-16_15.12",
"yyyy-MM-dd-HH_mm.ss",
CultureInfo.InvariantCulture,
DateTimeStyles.None)

You may want to use DateTime.ParseExact as this will take a datetime format pattern as a parameter.
DateTime.ParseExact

How to convert date format to DD-MM-YYYY in C#

How to convert date format to DD-MM-YYYY in C#? I am only looking for DD-MM-YYYY format not anything else.

string formatted = date.ToString("dd-MM-yyyy");
will do it.
Here is a good reference for different formats.

According to one of the first Google search hits:
http://www.csharp-examples.net/string-format-datetime/
// Where 'dt' is the DateTime object...
String.Format("{0:dd-MM-yyyy}", dt);

Here is the Simplest Method.
This is the String value: "5/13/2012"
DateTime _date;
string day = "";
_date = DateTime.Parse("5/13/2012");
day = _date.ToString("dd-MMM-yyyy");
It will output as: 13-May-2012

string formattedDate = yourDate.ToString("dd-MM-yyyy");

DateTime dt = DateTime.Now;
String.Format("{0:dd-MM-yyyy}", dt);

DateTime s1 = System.Convert.ToDateTime(textbox.Trim());
DateTime date = (s1);
String frmdt = date.ToString("dd-MM-yyyy");
will work

DateTime dt = DateTime.Now;
String.Format("{0:dd-MM-yyyy}", dt);

First convert your string into DateTime variable:
DateTime date = DateTime.Parse(your variable);
Then convert this variable back to string in correct format:
String dateInString = date.ToString("dd-MM-yyyy");

Here we go:
DateTime time = DateTime.Now;
Console.WriteLine(time.Day + "-" + time.Month + "-" + time.Year);
WORKS! :)

From C# 6.0 onwards (Visual Studio 2015 and newer), you can simply use an interpolated string with formatting:
var date = new DateTime(2017, 8, 3);
var formattedDate = $"{date:dd-MM-yyyy}";

Do you have your date variable stored as a String or a Date type?
In which case you will need to do something like
DateTime myDate = null;
DateTime.TryParse(myString,myDate);
or
Convert.ToDateTime(myString);
You can then call ToString("dd-MM-yyyy") on your date variable

I ran into the same issue. What I needed to do was add a reference at the top of the class and change the CultureInfo of the thread that is currently executing.
using System.Threading;
string cultureName = "fr-CA";
Thread.CurrentThread.CurrentCulture = new CultureInfo(cultureName);
DateTime theDate = new DateTime(2015, 11, 06);
theDate.ToString("g");
Console.WriteLine(theDate);
All you have to do is change the culture name, for example:
"en-US" = United States
"fr-FR" = French-speaking France
"fr-CA" = French-speaking Canada
etc...

The problem is that you're trying to convert a string, so first you should cast your variable to date and after that apply something like
string date = variableConvertedToDate.ToString("dd-MM-yyyy")
or
string date = variableConvertedToDate.ToShortDateString() in this case result is dd/MM/yyyy.

dateString = "not a date";
// Exception: The string was not recognized as a valid DateTime. There is an unknown word starting at index 0.
DateTime dateTime11; // 1/1/0001 12:00:00 AM
bool isSuccess2 = DateTime.TryParseExact(dateString, "MM/dd/yyyy", provider, DateTimeStyles.None, out dateTime11);

var dateTimeString = "21‎-‎10‎-‎2014‎ ‎15‎:‎40‎:‎30";
dateTimeString = Regex.Replace(dateTimeString, #"[^\u0000-\u007F]", string.Empty);
var inputFormat = "dd-MM-yyyy HH:mm:ss";
var outputFormat = "yyyy-MM-dd HH:mm:ss";
var dateTime = DateTime.ParseExact(dateTimeString, inputFormat, CultureInfo.InvariantCulture);
var output = dateTime.ToString(outputFormat);
Console.WriteLine(output);
Try this, it works for me.

you could do like this:
return inObj == DBNull.Value ? "" : (Convert.ToDateTime(inObj)).ToString("MM/dd/yyyy").ToString();