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How do I convert a date string from 'M/d/yyyy h:mm:ss tt' to 'yyyy-dd-mmTHH:mm:ss'? C#

I have a string that looks like 5/27/2015 4:49:54 AM
I need it to be in this format: 2015-27-05T04:49:54+08:00
I tried converting it like so but it throws an error:
var convertedDate = DateTime.ParseExact(originalDate, "yyyy'-'MM'-'dd'T'HH':'mm':'ss.fffffffK",
new CultureInfo("en-US", true));
I also tried converting it like this but it doesn't seem to do anything, convertedDate ends up being the same as originalDate:
var convertedDate = String.Format("{0:u}", originalDate);

You need to parse first, then use your desired format string with ToString translate.
Try this:
string input = "5/27/2015 4:49:54 AM";
DateTime originalDate = DateTime.Parse(input);
string output = originalDate.ToString("yyyy'-'MM'-'dd'T'HH':'mm':'ss.fffffffK");
You can swap out DateTime.Parse with DateTime.ParseExact if needed. DateTime.Parse will attempt to parse using your system culture. You can be more specific if you need/want to be.
Also, keep in mind that the f in the format string creates a mandatory decimal. To match your prescribed output, you should use F or omit.
https://msdn.microsoft.com/en-us/library/8kb3ddd4(v=vs.110).aspx

Try this code.
string inputString = "05/27/2015 04:49:54 AM";
DateTime dt = DateTime.ParseExact(inputString, "M/dd/yyyy H:mm:ss tt",
System.Globalization.CultureInfo.InvariantCulture);
string outputString = dt.ToString("yyyy-MM-ddTHH:mm:sszzz");
Output string will return the value as "2015-05-27T04:49:54+08:00".

First parse the original string to a DateTime. Then format the DateTime to a string of the desired format.
var originalDate = "5/27/2015 4:49:54 AM";
var result = DateTime.ParseExact(originalDate, "M/d/yyyy h:mm:ss tt", CultureInfo.CurrentCulture)
.ToString("yyyy'-'MM'-'dd'T'HH':'mm':'sszzzz");
Console.WriteLine(result);
Outputs
2015-05-27T04:49:54-04:00
Note that that the timezone offset you get will be dependent on the culture of the machine this runs on because it is not specified in the original string.

Try convertedDate.ToString("yyyy-MM-ddThh:mm:sszzz"), date and time settings on your local machine may affect how the output is formatted so you can't always rely on the in-built formatting strings.

To parse "5/27/2015 4:49:54 AM" you should use this format string: "M/d/yyyy h:mm:ss tt"
DateTime convertedDate = DateTime.ParseExact(
"5/27/2015 4:49:54 AM",
"M/d/yyyy h:mm:ss tt",
new CultureInfo("en-US", true));
Then you can use DateTime.ToString with the desired format-string which seems to be "yyyy-dd-MM'T'hh:mm:sszzz" to get 2015-27-05T04:49:54+08:00 as output:
string result = convertedDate.ToString("yyyy-dd-MM'T'hh:mm:sszzz"); // zzz to get UTC offset
See: The "zzz" Custom Format Specifier

How to Convert a string "dd/mm/yyyy HH:MM:SS" to "HH:MM" for on-line Test Duration?

Code :-
public string TestDuration { get; set; }
TestDuration =DateTime.Parse(dr.TestDuration.ToString()).ToShortTimeString() ;
I have a string of the format dd/mm/yyyy HH:MM:SS am/pm, it display date and time in my view, I need hours and minutes for online test duration in format hh:mm.
Example: testduration= 2hr or 2:30 mins

i have a string of type DateTime
That's not possible. You either have string or have DateTime. Your variable type can't be both of them.
You can format your DateTime with HH:mm format like;
var result = DateTime.Parse(dr.TestDuration.ToString())
.ToString("hh:mm", CultureInfo.InvariantCulture);
You didn't mentioned it but, on the other hand, your dr.TestDuration already might be a DateTime. You might wanna format this value instead to generate it's string representation, parsing it to DateTime and generate it's string representation again.
var result = dr.TestDuration.ToString("hh:mm", CultureInfo.InvariantCulture);
After your edit:
Since your TestDuration string and it has "dd/MM/yyyy HH:mm:ss tt" format, you need to parse it to DateTime and generate it's string representation with hh:mm format.
TestDuration = DateTime.ParseExact(dr.TestDuration, "dd/MM/yyyy HH:mm:ss tt",
CultureInfo.InvariantCulture)
.ToString("hh:mm", CultureInfo.InvariantCulture);

How to convert a date string from "dd-MMM-yy" to "M/dd/yyyy hh:mm:ss tt"?

I need to compare two date format strings:
dateString in "dd-MMM-yy" format
with
referenceDateString in "M/dd/yyyy hh:mm:ss tt" format respectively.
For that, I need to convert the dateString = "dd-MMM-yy" to "M/dd/yyyy hh:mm:ss tt".
However, Got an error while trying to do that:
"Error: string was not recognized as a valid datetime".
The C# code I used given below.
string dateString = "19-Dec-14";
string AsofDate = DateTime.ParseExact(dateString, "M/dd/yyyy hh:mm:ss tt", CultureInfo.InvariantCulture);
Edit 1:
In the actual code the dateString obtaining after reading a csv file which is supplied as "19-Dec-14", that's why it's in the string format.
Please help, am pretty new to C#. Thanks.

Habib already gave the answer on his comments, I try to add it as an answer;
From DateTime.ParseExact(String, String, IFormatProvider)
Converts the specified string representation of a date and time to its
DateTime equivalent using the specified format and culture-specific
format information. The format of the string representation must match
the specified format exactly.
In your case, clearly they don't. First, you need to parse your string to DateTime with proper format (which is dd-MMM-yy with an english-based culture), then you can get the string represention of your DateTime with specific format.
string s = "19-Dec-14";
DateTime dt;
if(DateTime.TryParseExact(s, "dd-MMM-yy", CultureInfo.InvariantCulture,
DateTimeStyles.None, out dt))
{
dt.ToString("M/dd/yyyy hh:mm:ss tt", CultureInfo.InvariantCulture).Dump();
// Result will be 12/19/2014 12:00:00 AM
}

It's not entirely clear what you are trying to do, but in order to parse that date you have on the first line, you would use something like this:
DateTime AsofDate = DateTime.ParseExact(dateString, "dd-MMM-yy", System.Globalization.CultureInfo.InvariantCulture);
Note a couple things here: I've changed the data type of AsofDate from string to DateTime because that's what DateTime.ParseExact returns. Also, I've modified the custom format string to match the format of the string you are trying to parse as a date ("19-Dec-14").

Convert custom date to mysql datetime

I have a custom date format that I want to convert to Datetime so I can then insert into my database, I tried using Datetime.ParseExact() But I think I'm misunderstanding something as the code throws a System.FormatException.
I have the following date format from a csv
> 6/11/2014 9:00
and I wish to convert it to the mysql datetime format
> 0000-00-00 00:00:00 OR yyyy-MM-dd HH:mm:ss
Notice they haven't included the seconds in the original date so I am unsure (without appending them to the end) how to set all records to just have "00" for seconds as it is not available.
I tried the following which throws an exception
DateTime myDate = DateTime.ParseExact("6/11/2014 9:00", "yyyy-MM-dd HH:mm",
System.Globalization.CultureInfo.InvariantCulture);

first thing you need to convert string to date time and than convert datetime tos tring
string strd = "6/11/2014 9:00";
DateTime dt ;
//convert datetime string to datetime
if(DateTime.TryParse(strd, out dt))
{
//convert datetime to custom datetime format
Console.WriteLine("The current date and time: {0: yyyy-MM-dd HH:mm:ss}",
dt); ;
}
output

I know this is late to answer that but I'm really surprised none of answer consider to use IFormatProvider to prevent a possible parsing error because of / format specifier or considering your string is a standard date and time format for your CurrentCulture or not so you can or can't use DateTime.TryParse(string, out DateTime) overload directly.
First of all, let's look at what DateTime.ParseExact documentation says:
Converts the specified string representation of a date and time to its
DateTime equivalent. The format of the string representation must
match a specified format exactly or an exception is thrown.
In your case, they don't match. You should use d/MM/yyyy H:mm format to parse your example string with a culture that have / as a DateSeparator. I almost always suggest to use DateTime.TryParseExact method in this kind of situations;
string s = "6/11/2014 9:00";
DateTime dt;
if(DateTime.TryParseExact(s, "d/MM/yyyy H:mm", CultureInfo.InvariantCulture,
DateTimeStyles.None, out dt))
{
Console.WriteLine(dt.ToString("yyyy-MM-dd HH:mm:ss"));
// result will be 2014-11-06 09:00:00
}

If you know formats of your dates, then you can do this:
string stringDate = "6/11/2014 9:00";
//Your date formats of input
string[] dateFormats = new string[]
{
"d/MM/yyyy H:mm",
"dd/MM/yyyy H:mm",
"dd/MM/yyyy HH:mm",
"dd/MM/yyyy H:mm:ss",
"dd/MM/yyyy HH:mm:ss"
/* And other formats */
};
DateTime convertedDate;
bool isSuccessful = DateTime.TryParseExact(stringDate, dateFormats,
System.Globalization.CultureInfo.InvariantCulture, System.Globalization.DateTimeStyles.None, out convertedDate);
if (isSuccessful)
{
//If conversion was successful then you can print your date at any format you like
//because you have your date as DateTime object
Console.WriteLine(convertedDate.ToString("dd-MM-yyyy HH:mm:ss")); /* Or other format you want to print */
}
I hope it will be helpful to you.

Datetime format Issue: String was not recognized as a valid DateTime

I want to format the input string into MM/dd/yyyy hh:mm:ss format in C#.
The input string is in format MM/dd/yyyy hh:mm:ss
For example :"04/30/2013 23:00"
I tried Convert.ToDateTime() function, but it considers 4 as date and 3 as month which is not what I want. Actually month is 04 and date is 03.
I tried DateTime.ParseExact() function also, But getting Exception.
I am getting error:
String was not recognized as a valid DateTime.

Your date time string doesn't contains any seconds. You need to reflect that in your format (remove the :ss).
Also, you need to specify H instead of h if you are using 24 hour times:
DateTime.ParseExact("04/30/2013 23:00", "MM/dd/yyyy HH:mm", CultureInfo.InvariantCulture)
See here for more information:
Custom Date and Time Format Strings

You can use DateTime.ParseExact() method.
Converts the specified string representation of a date and time to its
DateTime equivalent using the specified format and culture-specific
format information. The format of the string representation must match
the specified format exactly.
DateTime date = DateTime.ParseExact("04/30/2013 23:00",
"MM/dd/yyyy HH:mm",
CultureInfo.InvariantCulture);
Here is a DEMO.
hh is for 12-hour clock from 01 to 12, HH is for 24-hour clock from 00 to 23.
For more information, check Custom Date and Time Format Strings

try this:
string strTime = "04/30/2013 23:00";
DateTime dtTime;
if(DateTime.TryParseExact(strTime, "MM/dd/yyyy HH:mm",
System.Globalization.CultureInfo.InvariantCulture,
System.Globalization.DateTimeStyles.None, out dtTime))
{
Console.WriteLine(dtTime);
}

This can also be the problem if your string is 6/15/2019. DateTime Parse expects it to be 06/15/2019.
So first split it by slash
var dateParts = "6/15/2019"
var month = dateParts[0].PadLeft(2, '0');
var day = dateParts[1].PadLeft(2, '0');
var year = dateParts[2]
var properFormat = month + "/" +day +"/" + year;
Now you can use DateTime.Parse(properFormat, "MM/dd/yyyy"). It is very strange but this is only thing working for me.

change the culture and try out like this might work for you
string[] formats= { "MM/dd/yyyy HH:mm" }
var dateTime = DateTime.ParseExact("04/30/2013 23:00",
formats, new CultureInfo("en-US"), DateTimeStyles.None);
Check for details : DateTime.ParseExact Method (String, String[], IFormatProvider, DateTimeStyles)

DateTime dt1 = DateTime.ParseExact([YourDate], "dd-MM-yyyy HH:mm:ss",
CultureInfo.InvariantCulture);
Note the use of HH (24-hour clock) rather than hh (12-hour clock), and the use of InvariantCulture because some cultures use separators other than slash.
For example, if the culture is de-DE, the format "dd/MM/yyyy" would expect period as a separator (31.01.2011).

Below code worked for me:
string _stDate = Convert.ToDateTime(DateTime.Today.AddMonths(-12)).ToString("MM/dd/yyyy");
String format ="MM/dd/yyyy";
IFormatProvider culture = new System.Globalization.CultureInfo("fr-FR", true);
DateTime _Startdate = DateTime.ParseExact(_stDate, format, culture);

You may use this type format (get formatted data from sql server)
FORMAT(convert(datetime,'16/04/2018 10:52:20',103),'dd/MM/yyyy HH:mm:ss', 'en-us')
CONVERT(VARCHAR,convert(datetime,'16/04/2018 10:52:20',103), 120)