DateTime dt = DateTime.ParseExact("1122010", "Mddyyyy", System.Globalization.CultureInfo.CurrentCulture);
Throwing this exception: String was not recognized as a valid DateTime.
I'm sure it's the lack of a leading 0 in the month. What's the correct format string?
I suggest using the format "MMddyyyy" and ensuring your input parameter has at least 8 characters. Example:
DateTime dt = DateTime.ParseExact("1122010".PadLeft(8, '0'), "MMddyyyy", System.Globalization.CultureInfo.CurrentCulture);
If you are using a data source with the leading 0 missing for the month, this will add it where required.
The problem is that you are not giving ParseExact enough information to work with.
"M" means a 1 or 2 digit month. But your string starts with "1122". Is that January 12th or November 22nd?
The only solution, as Anthony shows, is to pad with a 0 when needed.
The single "M" format string is unacceptable because not all months can be uniquely represented with a single digit or character. As previously suggested, you will have to use "MMddyyyy" and pad the left string when necessary.
Related
var date= DateTime.ParseExact("16-03-2022 1:30", "dd-MM-yyyy HH:mm", CultureInfo.InvariantCulture);
When I enter 16-03-2022 13:30, it does not give an error but when the parameter is 16-03-2022 1:30, I get an error, how can I solve it?
I feel like taking a risk to answer but..
Let's go step by step. One of the good things about .NET methods is that you can see what exceptions can be thrown on that method in their documentation.
From "Exception" section on documentation it says;
FormatException
s or format is an empty string.
-or-
s does not contain a date and time that corresponds to the pattern
specified in format.
-or-
The hour component and the AM/PM designator in s do not agree.
Your s or format is not empty, your string does not have any AM or PM designator, so the only option left is "s does not contain a date and time that corresponds to the pattern specified in format." as a reason.
Also from documentation, it says;
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.
What "format" we are talking about? There are two of them. Custom date and time format strings and Standard date and time format strings. Since we are using DateTime.ParseExact, we need to consider using custom date and time format.
Let's look at all parts can be parse in your 16-03-2022 1:30 string;
16 --> Two digit day number (dd)
03 --> Two digit month number with leading zero (MM)
2022 --> Four digit year (yyyy)
1 --> One digit hour (it can be h or H because there is no time designator in your string and we can't know it's in 12-hour clock format or 24-hour clock format)
30 --> Two digit minutes (mm)
So, the proper format of your 16-03-2022 1:30 string can be either dd-MM-yyyy H:mm or dd-MM-yyyy h:mm which depends on you. If it is 24-hour format, use H specifier, if it is 12-hour format, use h specifier.
When you see the word "Exact" in ParseExact(), it means it. Any deviation from the expected format at all will cause an exception.
In this case, the HH specifier is not an exact match for the 1 value for the hour. It would match if you had 01 instead, but just 1 isn't the same thing. To match the hours without leading zeros you need a single H, creating this format string:
dd-MM-yyyy H:mm
This will still match later hours like "10" and "11". Additionally, the capital "H" instead of lower-case means it still expects 24-hour time, so numbers like "13" up to "23" still work, too.
If you could get a mix of values, that sometimes has just the 1 and sometimes might have the full 01, then you need to use a ParseExact() overload that accepts an array of formats, and provide both versions.
I want to be able to parse strings of time (hours, minutes, seconds) where the hours run from 0 to 23, and where the preceding zero for one-digit hours is optional.
Examples of time strings that I want to be able to parse into valid DateTime objects:
212540
061525
94505
I am trying to use the C# method DateTime.ParseExact to manage the parsing, but I cannot for the life of it come up with a format string that can handle the "single-digit hour without preceding zero" scenario.
How should I specify the DateTime.ParseExact format string to sufficiently parse all examples above with the same line of code?
Inspired by the MSDN page on custom date and time formats, I have tried the following approaches:
DateTime.ParseExact(time_string, "Hmmss", CultureInfo.InvariantCulture);
DateTime.ParseExact(time_string, "%Hmmss", CultureInfo.InvariantCulture);
DateTime.ParseExact(time_string, "HHmmss", CultureInfo.InvariantCulture);
All these format strings work for the first two example cases above, but faced with a single-digit hour and no preceding zero, all formulations throw a FormatException.
You can insert delimiters between hours, minutes and seconds like this:
string timeString = "94505";
string formatedTimeString = Regex.Replace(str, #"\d{1,2}(?=(\d{2})+$)", "$&:");
var datetime = DateTime.ParseExact(formatedTimeString, "H:mm:ss", CultureInfo.InvariantCulture);
UPDATE:
I've found the cause of failure when parsing "94505" with format string "Hmmss":
What's happening is that H, m and s actually grabs two digits when they can, even if there won't be enough digits for the rest of the format. So the for example with the format Hmm and the digits 123, H would grab 12 and there would only be a 3 left. And mm requires two digits, so it fails.
So basically you have two options for handling the "single-digit hour without preceding zero" scenario:
Change time format: place hours to the end (for example, "ssmmH" or "mmssH") or use delimiters (for example, "H:mm:ss")
Modify the string like I've suggested earlier or like keyboardP has.
You could pad your input string if you know that you'll always have six characters.
string input = "94505";
if(input.Length < 6)
input = input.PadLeft(6, '0');
(Or use input.Length == 5 if you have other valid formats that are shorter).
What about using:
DateTime.ParseExact(time_string, "Hmmss", CultureInfo.InvariantCulture).ToString("HH:mm:ss")
I'm trying to find the appropriate format string to parse (exact) the following types of dates:
1-01-01T00:00:00+00:00 - 1 January of 0001
2011-12-14T15:53:40+00:00 - 14 December of 2011
So the year length seems to be variable (1-4 characters).
The format sting I currently use to parse exact is:
c_DateTimeFormatString = "yyyy-MM-ddTHH':'mm':'sszzz"
Obviously this only matches the second string. The first one poped up today. Now we have to match that as well.
Is there a format string to achieve this?
UPDATE #1
I added the actual dates in clear text after the input date strings.
UPDATE #2
Parse exact has an overload that allows for multiple format strings to be passed in. This seems to be the right way.
So the first try was to use:
DateTime.ParseExact("1-01-01T00:00:00+00:00 ", new[] { "yyyy-MM-ddTHH':'mm':'sszzz", "yyy-MM-ddTHH':'mm':'sszzz", "yy-MM-ddTHH':'mm':'sszzz", "y-MM-ddTHH':'mm':'sszzz" }, CultureInfo.CreateSpecificCulture("en-US"), DateTimeStyles.AssumeLocal)
But sadly this does ont give the correct result, the first date string is parsed as:
01.01.2001
rather than
01.01.0001
So the question now is what is the correct parsing string to parse year one which is represented with only one digit?
Updated based on comment:
string y = "yyyy-MM-ddTHH':'mm':'sszzz";
string testDate = "1-01-05T00:00:00+00:00".PadLeft(25, '0');
Console.WriteLine(DateTime.ParseExact(testDate, y, CultureInfo.InvariantCulture));
testDate = "2011-12-14T15:53:40+00:00".PadLeft(25, '0');
Console.WriteLine(DateTime.ParseExact(testDate, y, CultureInfo.InvariantCulture));
The output is:
1/5/0001 00:00:00
12/14/2011 15:53:40
You can use an overload of ParseExact to match multiple formats, I believe.
See MSDN.
If the input formats are not all exactly the same, you'll need either to stop using parse exact, or to call it with different format arguments depending on the format of the input data.
I don't believe you need to match a year from 1 to 4 characters but 2 or 4 characters.
For this example
1-01-05T00:00:00+00:00
you would need something like
d-MM-yyTHH':'mm':'sszzz
Try padding your string so that the year is 4 digits long. You should probably add 2, 20 or 201 and not just 0's.
Since you know that you have to support multiple formats, I suggest that you use the TryParseExact method.
If it fails to parse using one format (i.e. it returns false), then try the next format.
Can anyone explain why the following snippet returns true?
According to the docs for The "d" custom format specifier, "A single-digit day is formatted without a leading zero." So why doesn't TryParseExact fail when I give it a single-digit day with a leading zero?
DateTime x;
return DateTime.TryParseExact
(
"01/01/2001",
#"d\/MM\/yyyy",
null,
System.Globalization.DateTimeStyles.None,
out x
);
UPDATE
I think maybe I was unclear originally. What I am really trying to get at is: Why does TryParseExact accept some values that don't match exactly? from all of the documentation I have seen, 'd' matching '01' and '1' is just as much a bug as if 'MM' matched 'March' as well as '03'. The issue here isn't that the values are equivalent, its that they don't match the format.
The relevant snippets of documentation are:
From TryParseExact: The format of the string representation must match a specified format exactly.
From The 'd' Specifier: A single-digit day is formatted without a leading zero.
It seems abundantly clear to me that '01' has a leading 0, and therefore doesn't exactly match 'd'.
From the .NET 4 source in DateTimeParse.ParseByFormat():
case 'd':
// Day & Day of week
tokenLen = format.GetRepeatCount();
if (tokenLen <= 2) {
// "d" & "dd"
if (!ParseDigits(ref str, tokenLen, out tempDay)) {
if (!parseInfo.fCustomNumberParser ||
!parseInfo.parseNumberDelegate(ref str, tokenLen, out tempDay)) {
result.SetFailure(ParseFailureKind.Format, "Format_BadDateTime", null);
return (false);
}
}
if (!CheckNewValue(ref result.Day, tempDay, ch, ref result)) {
return (false);
}
}
else
{...}
The parser lumps "d" and "dd" together.
It appears that behavior is by design, and I think it works that way to be consistent with other string formatting options.
Take the following example:
//Convert DateTime to string
string dateFormat = "d/MM/yyyy";
string date1 = new DateTime(2008, 10, 5).ToString(dateFormat);
string date2 = new DateTime(2008, 10, 12).ToString(dateFormat);
//Convert back to DateTime
DateTime x1, x2;
DateTime.TryParseExact(date1, dateFormat, null, System.Globalization.DateTimeStyles.None, out x1);
DateTime.TryParseExact(date2, dateFormat, null, System.Globalization.DateTimeStyles.None, out x2);
Console.WriteLine(x1);
Console.WriteLine(x2);
In the first part, ToString() outputs a two digit day for October 12th, because it wouldn't make much sense to just write out a single digit day (and which digit would it pick, the 1 or the 2?). So since the "d" represents one OR two digit days when converting to a string, it would have to work the same way when converting back to DateTime. If it didn't, the conversion back to DateTime in TryParseExact in my example would fail, and that would definitely not be an expected behavior.
I would say that if you really need to match a d/MM/yyyy format exactly, you could probably use a regex to validate the string and then pass it through Parse, TryParse or TryParseExact (depending on how good your regex is, since it would have to handle leap years, 30/31 days, etc if you wanted to use Parse).
I'd say it doesn't fail because TryParseExact is smart enough to know that '01' == '1'.
TryParseExact is just trying to be flexible in this case I guess. But the "d" vs "dd" should and would work as advertised when you are converting date to string using a format specifier.
Because a single 'd' means that your DateTime value will be converted to as short value as possible, i.e. without leading zero if there's no necessity for it. I suppose it shouldn't fail when you're converting from string to DateTime because the main purpose of TryParseExact's format string is to help to convert to DateTime, i.e. it serves like a hint, it's not intended to validate string format.
You can use RegEx if you still need hardcore string format validation.
For the following code, I would expect result to equal 2, because the MSDN states that 'd' "Represents the day of the month as a number from 1 through 31. A single-digit day is formatted without a leading zero.".
DateTime myDate = new DateTime( 2009, 6, 4 );
string result = myDate.ToString( "d" );
However, result is actually equal to '6/4/2009' - which is the short-date format (which is also 'd'). I could use 'dd', but that adds a leading zero, which I don't want.
To indicate that this is a custom format specifier (in contrast to a standard format specifier), it must be two characters long. This can be accomplished by adding a space (which will show up in the output), or by including a percent sign before the single letter, like this:
string result = myDate.ToString("%d");
See documentation
Rather than using string formatting strings, how about using the Day property
DateTime myDate = new DateTime(2009,6,4)
int result = myDate.Day;
Or if you really needed the result in string format
string result = myDate.Day.ToString();
If you are looking to get a specific date part out of a date object rather than a formatted representation of the date, I prefer to use the properties (Day, Month, Year, DayOfWeek, etc.) It makes reading the code a bit easier (particularly if someone else is reading/maintaining it that doesn't have the various formatting codes memorized)