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Convert date time string in dd/mm/yyyy to datetime format mm/dd/yyyy

There is an input from CSV file which is in dd/mm/yyyy format.
I have to pass these date values to the stored procedure.
I want to convert this to mm/dd/yyyy format before I bulkcopy it to the database table from the datatable in the c# code.
Should I do this in the code or in the stored procedure which I am sending it to?
Please advise.I have tried all possible combinations.

You could you use DateTime.ParseExact,
var parsedDate = DateTime.ParseExact(dateString, "dd/MM/YYYY", CultureInfo.InvariantCulture);
where dateString is the string representation of the date you want to parse.
If your stored procedures expects a DateTime you could use the parseDate value. Otherwise, if it expects a string in the format you mentioned, you can pass the following value:
parsedDate.ToString("MM/dd/YYYY")

You should parse your value to DateTime in C# and pass this date value to your SQL client or ORM without converting it to a string

If your SQL column type is set to either one of the date value types it is quite impossible to format the date according to your desire, since the database engine does not store the formatted value but the date value itself.
Make sure to parse the DateTime in-code before updating its value in the SQL database.
string date = "2000-02-02";
DateTime time = DateTime.Parse(date); // Will throw an exception if the date is invalid.
There's also the TryParse method available for you. It will make sure the date value you're trying to parse is indeed in the right format.
string input = "2000-02-02";
DateTime dateTime;
if (DateTime.TryParse(input, out dateTime))
{
Console.WriteLine(dateTime);
}
After the storage you're more than welcome to select your preferred display format for your DateTime variable using one of the given formats (read link below for a full list of available formats).
https://msdn.microsoft.com/en-us/library/8kb3ddd4(v=vs.110).aspx

remove time from date and print only date in datetime format

i have date stored in a string format as follows: "2014-03-12"
im passing this to a database which accepts the date as datetime.
im converting the string date to datetime format as follows:
DateTime StartDates = Convert.ToDateTime(StartDate);
but the time gets appended along with the date as "2014-03-12 12:00:00:00"
can anyone tel me how to send only the date leaving out the time.
i want the final date to be still in datetime format only but with time part cut off

DateTime is irrespective of the format. Formatting is only useful for presentation purpose. A DateTime object will have a Date part and Time part. When you try parsing your string "2014-03-12", it doesn't have a Time part, so in the parsed object, Time is set to 00:00:00.
If you just want to to display date then you can use DateTime.ToShortDateString method or use a custom format like:
string formattedDateString = StartDates.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture);

If you're happy with the date part, you may simply return the Date property of the DateTime conversion result:
DateTime StartDates = Convert.ToDateTime(StartDate).Date;
I should mention that using Convert.ToDateTime puts you at the mercy of the process current culture date format though, so you probably want to use the ParseExact or ToString method like the other answers suggests, with the appropriate format and culture instance.

SQL datetime to C# string and back to SQL datetime

I have a webservice method that gets data from sql of the format
2012-11-18 11:21:03 when i save it to C# string it becomes this format: 18.11.2012 11:21:03
How do i change it back to the SQL format 2012-11-18 11:21:03 ?

Parse it into a dateTime again
DateTime myTime = DateTime.Parse(myString);
and back into a proper to string
myTime.ToString("yyyy-MM-dd HH:mm:ss");
Or just read it into a datetime and cut out the middleman.

You can get the universally sortable string format (which looks like the one used by SQL server) by using the format string "u" like this:
var dateTimeString = String.Format("{0:u}", yourDateTime);

Simply run the below code,
var newDateTime = oldDateTime.Date.ToString("yyyy-MM-dd HH:mm:ss");
Its just converting it back to the SQL Format DATETIME

Trouble with Dates as strings is they are ambiguous and the formats can vary based on where you are in the world, or even local machine settings. You might assume a date string is yyyy-mm-dd but what if it is actually yyyy-dd-mm? Some dates will appear to work and some will be invalid.
In other words is 2013-02-10 the 10th of February or is it the 2nd of October? If it is just a string you have no way of knowing for sure what was intended.
Your best bet as suggested by #Haedrian is to store in a DateTime C# object, not a string. That way it is never ambiguous and you have access to various date specific functions. If you must store as a string you can convert back to a date as above or use
DateTime.TryParse(datestring, out dateVariable);
which won't throw an exception for an invalid format. Depends if you want exceptions!
Also I would suggest if you must use strings to use a 3 character month in strings, which again eliminates the ambiguity, e.g.
"dd-MMM-yy hh:mm tt"

Changing the format of date

I have a DateTime variable (say, timestamp) that holds a date in its usual format like this:
11/1/2011
This variable is used to build a SQL command. The Oracle database only accepts dates in the format
YYYY-MM-DD
How can I manipulate my variable to store the date in this format?

Don't format the date to include it in SQL at all.
Use a parameterized query, and then just include the value as a parameter. That way you don't have to get any formatting right at all.
You should use parameterized queries for all data - aside from formatting, it also protects you from SQL injection attacks.
Getting a date/time format which works for the particular installation of Oracle you're using right now is not the right fix. Do it properly: avoid including data in your code (the SQL).
On a different matter, your question is making incorrect assumptions to start with. A DateTime variable doesn't hold value in a "usual format" at all, any more than an int holds a decimal representation or a hex representation of a number. DateTime doesn't store text internally at all - it stores a number of ticks. How it is formatted when you call ToString depends on all kinds of cultural aspects. It's worth separating the notion of the fundamental value represented by a type from the formatted string representation you might happen to obtain by calling ToString.

I assume you send the date as string in the SQL command.
DateTime date = ...your object...;
string formattedDate = date.ToString("yyyy-MM-dd");
If it´s in string format, then you need to parse it first. It´s hard to see from your string if it´s day/month/year or month/day/year.
But you could do something like this:
string sDateTime = "11/1/2011";
DateTimeFormatInfo format = new DateTimeFormatInfo();
format.ShortDatePattern = "dd/MM/yyyy"; // or MM/dd/yyyy
DateTime date = DateTime.Parse(sDateTime, format);
string formattedDate = date.ToString("yyyy-MM-dd");

var dt = DateTime.Now;
var formatted = dt.ToString("yyyy-MM-dd");

Try this:
string oracleTimeFomatDate = DateTime.Now.ToString("yyyy-MM-dd")

Convert DateTime to string with format YYYYMMDD

I have birth dates stored as datetime in SQL Server 2008 like so:
2010-04-25 00:00:00.000
What is the best way, using C#, to convert and format this into a string with a YYYYMMDD format?
In the end, all I need is a string like:
20100425
Any help is greatly appreciated!

date.ToString("yyyyMMdd");
Should be what you need.

You need to get that value into a DateTime object and then you can use it's ToString() function like so:
.ToString("yyyyMMdd");

Are you able to get the data out of the database as a DateTime (.NET) object? If so, you can use the DateTime's instancename.ToString("yyyyMMdd")
If you haven't gotten to that stage yet, there's quite a few different ways to get the data out. It's a whole Google search in itself...

You just format the date using a custom format string:
string formatted = theDate.ToString("yyyyMMdd");
Note that the date doens't have a format at all when it's stored as a datetime in the database. It's just a point in time, it doesn't have a specific text representation until it's specifically created from the date.

Use the .ToString() method on the date time object, and pass in the format you want.