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C#: Is this possible to convert 24hrs format string Datetime to 12hrs AM/PM dateformat (again in string only)

I have a date/time return from a C# method is in string,
string dateTime = "2018-6-18 20:50:35"
Now I would like to convert this into another string representation like,
string convertDT = "2018-6-18 08:50:35 PM"
Is this possible?
Seems like I can do something like,
var formattedTime = dateTime.ToString("h:mm tt", CultureInfo.InvariantCulture);
but not working. Suggestion please!

Just parse the string into a new DateTime object and then call ToString() with the right formats:
string dateTime = "2018-6-18 20:50:35";
DateTime parsedDateTime;
if(DateTime.TryParse(dateTime, out parsedDateTime))
{
return parsedDateTime.ToString("yyyy-M-d hh:mm tt");
}
The benefit of my answer is that it contains validation (DateTime.TryParse()), it results in a couple extra lines of code but you can now accept all input and not worry about an exception being thrown.
Even better would be to refactor this logic into its own method that you can re-use:
public static bool TryChangeDateTimeFormat(string inputDateString, string outputFormat, out string outputDateString)
{
DateTime parsedDateTime;
if(DateTime.TryParse(inputDateString, out parsedDateTime))
{
outputDateString = parsedDateTime.ToString(outputFormat);
return true;
}
outputDateString = string.Empty;
return false;
}
This returns a bool of whether or not the conversion was successful and the out variable will be modified depending on the result.
Fiddle here

Without adding any validation,
var string24h = "2018-6-18 20:50:35";
var dateTime = DateTime.Parse(string24h);
var formattedTime = dateTime.ToString("h:mm tt", CultureInfo.InvariantCulture);

Use DateTime.ParseExact and then ToString

Sure, you can use the DateTime class to parse the original string and then output a differently formatted string for the same date:
string result = DateTime.Parse(dateTime).ToString("h:mm tt", CultureInfo.InvariantCulture);

var dateTime = "2018-6-18 20:50:35";
var dt = Convert.ToDateTime(dateTime);
var amPmDateTime = dt.ToString(#"yyyy-MM-dd hh:mm:ss tt", CultureInfo.InvariantCulture);

To give you exactly your format you would use
string convertDT = DateTime.Parse(dateTime).ToString("yyyy-MM-dd hh:mm:ss tt");
You can change the format between the quotes however you would like. For example yyyy/MM/dd or something. Just remember MM is 2 spots for months and mm is 2 spots for minutes.
So if you put
string convertDT = DateTime.Parse(dateTime).ToString("yyyy-mm-dd hh:mm:ss tt");
You are going to get year - minutes - days.

how to get the date from string in C#

I have a string like
string startdatestring = "2017-03-10T07:19:28.907";
DateTime firstdate = DateTime.ParseExact(startdatestring,
"yyyy/MM/dd hh:mm:ss",
CultureInfo.InvariantCulture);
var firstDateString = firstdate.ToString("yyyy-MM-dd");
want the output only 2017-03-10

Modify your code like below
string startdatestring = "2017-03-10T07:19:28.907";
//1st way - Convert.ToDatetime works properly
//DateTime firstdate = Convert.ToDateTime(startdatestring);
//2nd way - DateTime.Parse also works perfect
//DateTime firstdate = DateTime.Parse(startdatestring);
//3rd way - DateTime.ParseExact also works perfect
DateTime firstdate = DateTime.ParseExact(startdatestring,
"yyyy-MM-ddTHH:mm:ss.fff",
CultureInfo.InvariantCulture);
var firstDateString = firstdate.ToString("yyyy-MM-dd");
Console.WriteLine(firstDateString);
OUTPUT
2017-03-10

Your input string "2017-03-10T07:19:28.907" doesn't match the format string "yyyy/MM/dd hh:mm:ss".
Considering your input is already in a standard format, you can use DateTime.Parse:
var firstdate = DateTime.Parse(startdatestring);

DateTime firstdate = DateTime.ParseExact(startdatestring,
"yyyy-MM-dd hh:mm:ss",
CultureInfo.InvariantCulture);
it's yyyy-MM-dd instead of yyyy/MM/dd
;)

Change you code as below
DateTime firstdate = DateTime.ParseExact(startdatestring,
"yyyy-MM-ddTHH:mm:ss.fff",
CultureInfo.InvariantCulture);

Do something like this
string startdatestring = "2017-03-10T07:19:28.907";
string s = startdatestring.Substring(0, 9);

Assign value of a string (containing date and time) to two different variable (one for Date and one for Time)

I have a string ("CompletionDate") which contains the value "2/28/2017 5:24:00 PM"
Now I have 2 variables (EDate and ETime). I want to assign the Date to EDate (i.e 2/28/2017) and Time to ETime (i.e. 5:24:00 PM).
How can I split the Date and Time from a single string.
Kindly Help.
My approach right now is like :
string CompletionDate = string.Empty;
string ProjectEDate = string.Empty;
string ProjectETime = string.Empty;
CompletionDate = "2017-03-29 12:58:00";
DateTime dt = DateTime.ParseExact(CompletionDate, "yyyy-MM-dd", CultureInfo.CreateSpecificCulture("en-us"));
DateTime dt1 = DateTime.ParseExact(CompletionDate, "HH:mm:ss", CultureInfo.CreateSpecificCulture("en-us"));
var ProjectEDate = dt.ToString();
var ProjectETime = dt1.ToString();
But its throwing exception that string is not in correct format. Kindly help

#Chris pointed one of your problems, but you have one more. You are passing full date time string and trying to treat it as date or time only, which is not true. Instead I suggest you to parse DateTime object with both date and time, and then take whatever you need from parsed object:
CultureInfo enUS = CultureInfo.CreateSpecificCulture("en-us");
DateTime dt = DateTime.ParseExact(CompletionDate, "yyyy-MM-dd HH:mm:ss", enUS);
var ProjectEDate = dt.Date.ToString();
var ProjectETime = dt.TimeOfDay.ToString();

You need to specify the full format as same as the input string to parse method.
DateTime dt = DateTime.ParseExact(CompletionDate, "yyyy-MM-dd HH:mm:ss", System.Globalization.CultureInfo.CreateSpecificCulture("en-us"));
To get results you can use below methods available by default in DateTime.
dt.ToShortTimeString()
"12:58 PM"
dt.ToLongTimeString()
"12:58:00 PM"
dt.ToLongDateString()
"Wednesday, March 29, 2017"
dt.ToShortDateString()
"3/29/2017"
Or you can specify the format to ToString method.
dt.ToString("yyyy-MM-dd")
"2017-03-29"
dt.ToString("HH:mm:ss")
"12:58:00"

DateTime.ParseExact(CompletionDate, "yyy-MM-dd", ...
You are missing 4th 'y' in date format string:
"yyyy-MM-dd"
^
here
and:
String was not recognized as a valid DateTime " format dd/MM/yyyy"

Why do you parse into DateTime and then convert to a string using ToString again? Couldn´t you just simply use String.Split when all you want is to split the time from the day and you know the exact format?
var CompletionDate = "2017-03-29 12:58:00";
var tmp = CompletionDate.Split(' ');
var ProjectEDate = tmp[0];
var ProjectETime = tmp[1];

Error when converting date to dd-MMM-yy

I am getting an error when I run the following line of code:
DateTime dt = DateTime.ParseExact(bolShipdate, "dd/MMM/yyyy", null);
The error is:
String was not recognized as a valid DateTime.
The bolShipdate value is 02-21-2016. I need to convert the date to 21-Feb-16.
How can I resolve this?

Your format in ParseExact needs to match your string. dd/MMM/yyyy doesn't match the sample data provided. try:
var bolShipdate = "02-21-2016";
DateTime dt = DateTime.ParseExact(bolShipdate, "MM-dd-yyyy", null);
Console.WriteLine(dt.ToString("dd-MMM-yy")); // Dispays 21-Feb-16
(Example fiddle)

Declaration of DateTime.ParseExact is
public static DateTime ParseExact(
string s,
string format,
IFormatProvider provider
)
Here you will want to pass the format you are parsing not the expected result. And it looks like your string is of the format MM-dd-yyyy.
You can then use .ToString(string format to get the date in your desired format:
string date = "02-21-2016";
DateTime dt = DateTime.ParseExact(date, "MM-dd-yyyy", CultureInfo.InvariantCulture);
string newFormat = dt.ToString("dd-MMM-yy");
Console.WriteLine(newFormat);

Hope this can resolve:
var date = "02-21-2016";
DateTime dt = DateTime.ParseExact(date, "MM-dd-yyyy", CultureInfo.InvariantCulture);
string result = dt.ToString("dd-MMM-yy");

C# string to SqlDateTime: how to set format for recognition?

I need to use
SqlDateTime.Parse(val)
where val is a string such as " 23.3.1992 00:00:00 ".
The string is in European format, that is, day precedes month. However Parse wants "American" format. How I can tell it to use particular datetime format / locale?
Thanks in advance!

Try this:
string val = "23.12.1992 00:00:00";
// Parse exactly from your input string to the native date format.
DateTime dt = DateTime.ParseExact(val, "dd.M.yyyy hh:mm:ss", null);
// Part to SqlDateTime then
System.Data.SqlTypes.SqlDateTime dtSql = System.Data.SqlTypes.SqlDateTime.Parse(dt.ToString("yyyy/MM/dd"));
This could be done in one statement, but just separated for illustration.

Have you tried DateTime instead of SQLDateTime
DateTime d = DateTime.Parse(val);
String s = d.ToString(CultureInfo.CreateSpecificCulture("en-US"));

Can you try this ?
string valInEuropean = "23.3.1992 00:00:00";
DateTime dateInEuropean = DateTime.Parse(valInEuropean);
string valInAmerican = dateInEuropean.ToString("yyyy-MM-dd HH:mm:ww");

For converting a string to datetime object when the format is known(in this case )
use
DateTime dwweek = DateTime.ParseExact("23.3.1992 00:00:00", "dd.MM.yyyy hh:mm:ss", System.Globalization.CultureInfo.InvariantCulture);