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Dateformat is right but getting String was not recognized as a valid DateTime

My dateformat is dd/MM/yyyy.
I have a date column in my file with values like 1/08/2019 to 31/08/2019.
But I'm getting the following error when processing that file:
System.FormatException: String was not recognized as a valid DateTime.
at System.DateTimeParse.ParseExact(String s, String format, DateTimeFormatInfo dtfi, DateTimeStyles style)

You've specified in your format string that the days and months must be double digits, but it appears that your input can be single digits.
In order to solve this, you need to specify a single digit in the format string by using a single d for the day portion (and a single M for the month, too).
It's also safe to use a single digit in the format string, since it will handle both single and double digits.
So your format string should look like: "d/M/yyyy"
For example, these all work:
var a = DateTime.ParseExact("1/8/2019", "d/M/yyyy", CultureInfo.CurrentCulture);
var b = DateTime.ParseExact("1/08/2019", "d/M/yyyy", CultureInfo.CurrentCulture);
var c = DateTime.ParseExact("01/8/2019", "d/M/yyyy", CultureInfo.CurrentCulture);
var d = DateTime.ParseExact("01/08/2019", "d/M/yyyy", CultureInfo.CurrentCulture);

difficult to say as you show the error but not the actual code, as you have dates in your file of differennt format, like d/MM/yyyy and dd/MM/yyyy try to use TryParse instead of ParseExact and if the TryParse fails with one format ( d/MM/yyyy ), then do another TryParse with the second format ( dd/MM/yyyy ) that way you should be able to cover both cases.
Again, without seeing the code it is difficult to give more detailed feedback.
also you could use an approach with TryParseExact and multiple format strings, like shown here:
var formatStrings = new string[] { "MM/dd/yyyy hh:mm:ss tt", "yyyy-MM-dd hh:mm:ss" };
if (DateTime.TryParseExact(dt, formatStrings, enUS, DateTimeStyles.None, out dateValue))
return dateValue;
see this SO answer: https://stackoverflow.com/a/17859959/559144

C#. String was not recognized as a valid DateTime

I have a string:
string date = "2019-06-06T14:31:55.7316366+03:00";
and I'm trying to map it to DateTime:
var formattedDate = DateTime.ParseExact(date, "dd/MM/yyyy", null)
But I have an exception: "String was not recognized as a valid DateTime."

I would recommend you to use TryParseExact that returns a boolean value indicating if the convert from string to DateTime is possible on a given format. In your case, the format "o" is valid because it includes everything you have on your pattern (see the links bellow). For sample:
string date = "2019-06-06T14:31:55.7316366+03:00";
DateTime dateValue;
if (DateTime.TryParseExact(date, "o", CultureInfo.InvariantCulture, DateTimeStyles.None, out dateValue))
{
// it works
Console.WriteLine("Converted '{0}' to {1} ({2}).", date, dateValue,
dateValue.Kind);
}
else
{
Console.WriteLine("Convertion fails");
}
See the working sample: https://dotnetfiddle.net/V8ftPI
You also can use the ParseExact like your original sample.
var formatedDate = DateTime.ParseExact(date, "o", null);
but it can throws an exception if the date string is not on a valid pattern.
Check these links on the documentation about the DateTime.TryParseExact and DateTime formats and see the valid dateTime formats for C# to extract the format you need.

Failing to parse date in yyyyMMdd Hmm format using DateTime.TryParseExact()

I am getting my date time in a format like "20170317 630"
which means 17 March 2017 6:30 am
Here is the code block I am trying, but it is failing.
var str = "20170317 0630";
var formatedTime = "yyyyMMdd Hmm";
DateTime etaDate;
if (!DateTime.TryParseExact(str,formatedTime, CultureInfo.InvariantCulture, DateTimeStyles.None, out etaDate)) //formatedTime, CultureInfo.InvariantCulture, DateTimeStyles.None
{
Console.WriteLine("Date conversion failed " + etaDate);
}
Console.WriteLine("Date conversion passed "+etaDate);
Passing for: 20170317 0630
Failing for: 20170317 630
Please help me with this.

I'm not entirely surprised it's failing to parse that - I suspect it's greedily parsing the "63" and deeming that to be an invalid hour number.
We have exactly the same problem in Noda Time - and I don't intend to fix it. Making this work would be a huge amount of effort, and quite possibly reduce the performance for more sensible formats.
I would strongly suggest moving to a more sensible format, e.g. one of
H:mm to remove the pseudo-ambiguity
HHmm to make it all clearer
HH:mm even better, IMO - preferrably with hyphens for date parts, so yyyy-MM-dd HH:mm
You can convert from one format to another by simply detecting the length of the string, as every other part of it is a fixed length. For example, to just move to using HHmm you can do:
if (str.Length == "yyyyMMdd Hmm".Length)
{
str = str.Insert("yyyyMMdd ".Length, "0");
}
Then parse with yyyyMMdd HHmm format. If the length isn't right for either valid width, then it will fail to parse later anyway.

//split str in to strDate and strTime by using space
var strDate = "20170317"; //Date part
var strTime ="630"; //Time part
if(strTime.Length ==3) //check lenght of time part
{
strTime = "0" + strTime; //Add extra zero
}
var formatedTime = "yyyyMMdd HHmm";
DateTime etaDate;
if (!DateTime.TryParseExact(strDate + strTime,formatedTime, CultureInfo.InvariantCulture, DateTimeStyles.None, out etaDate)) //formatedTime, CultureInfo.InvariantCulture, DateTimeStyles.None
{
Console.WriteLine("Date conversion failed " + etaDate);
}
Console.WriteLine("Date conversion passed "+etaDate);

For valid DateTime(Error shows string was not recognized )

I am trying to convert my string formated value to date type with format dd/MM/yyyy. It runs fine but when I enter fromdate(dd/MM/yyyy) in textbox its fine and todate(dd/MM/yyyy) in textbox then it gives an error that string was not recognized as a valid datetime.What is the problem exactly i dont know. same code run on another appliction its run fine but in my application it shows Error.
Below I have used array for required format and split also used.
string fromdate = punchin.ToString();
string[] arrfromdate = fromdate.Split('/');
fromdate = arrfromdate[1].ToString() + "/" + arrfromdate[0].ToString() + "/" + arrfromdate[2].ToString();
DateTime d1 = DateTime.Parse(fromdate.ToString());

try with DateTime.TryParseExact as below
DateTime date;
if (DateTime.TryParseExact(inputText, "MM/dd/yyyy",
CultureInfo.InvariantCulture,
DateTimeStyles.None,
out date))
{
// Success
}
if you know the format of input date time you don't need to do any string manipulation.
But you need to give correct Date and Time Format String

I got 5/13/2013 12:21:35 PM in string fromdate
Use DateTime.TryParseExact, You don't have to split your string based on / and then get first three items from the array instead you can simply do:
DateTime dt;
if (DateTime.TryParseExact("5/13/2013 12:21:35 PM",
"M/d/yyyy hh:mm:ss tt",
CultureInfo.InvariantCulture,
DateTimeStyles.None,
out dt))
{
//date is fine
}
Using single d and single M as it can accomodate single digit as well as double digits day/Month part. You can simply pass punchin as the string parameter, Calling ToString on string types is redundant.

Try :
DateTime.ParseExact(fromdate, "MM/dd/yy", CultureInfo.InvariantCulture)
Obviously you can reformat the above, and use different providers by creating an instance of CultureInfo related to the string you are parsing, and you can modify the format string to reflect that culture or to accommodate more date parts

Giving System.FormatException: String was not recognized as a valid DateTime. using datetime.ParseExact in C#

I am below code in c#, where I am converting my string type format date to datetime, but giving the error.
if (!string.IsNullOrEmpty(SessionDictionary.GetValue("UserDetails", "ExpiryDate")))
{
DateTime ExpiryDate = DateTime.ParseExact(SessionDictionary.GetValue("UserDetails", "ExpiryDate"), "dd mmm yy", null);
strDate = sitedata.FormatDate(ExpiryDate, TridionDateFormat.ShortDate);
}
else
{
strDate = "-";
}
My SessionDictionary.GetValue("UserDetails", "ExpiryDate") is string type data which returns "31/01/2011 00:00:00" format date, in above code where I am using DateTime.ParseExact it is giving me System.FormatException: String was not recognized as a valid DateTime. error.
Please suggest what is wrong.
Thanks.

The sample date you describe (31/01/2011 00:00:00) looks like a format dd/MM/YYYY HH:mm:ss, so why are you using dd mmm yyyy?
Try
DateTime.ParseExact(..., "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).

Probably because of mmm(there isn't such month format), try MMM instead.(looks like Feb/Jan/etc)

You are using the wrong format to parse the date. The correct one is:
DateTime ExpiryDate = DateTime.ParseExact(SessionDictionary.GetValue("UserDetails", "ExpiryDate"), "dd/MM/yyyy hh:mm:ss", null)
Also, if your system date format is set to dd/MM/yyyy you can simply use:
DateTime ExpiryDate = DateTime.ParseExact(SessionDictionary.GetValue("UserDetails", "ExpiryDate"), "G", null)

Try
DateTime ExpiryDate = DateTime.ParseExact(SessionDictionary.GetValue("UserDetails", "ExpiryDate"), "g", null);
or see here: http://msdn.microsoft.com/en-us/library/8kb3ddd4.aspx