I'm making a timecard program, where the user enters the start time, end time, and project name. They can click "Add" and it adds the entered details to a listbox.
I don't allow the data to be added unless the start time and end time are formatted like this: 08:14am It gets annoying, though, having to enter it exactly like that each time, so I decided to, via regexes, have it automatically format. So if you enter 8:14, it will change it to 08:14am. How can I accomplish this via Regex.Replace()?
If you have any other methods, don't hesitate to list them.
Edit 1: I also have other replacements in mind; for example 814 goes to 08:14am, and 8 goes to 08:00am
Edit 2: So Now I'm using this code:
string[] formats = { "h:mm", "h", "hh", "hmm", "hhmm", "h:mmtt", "htt", "hhtt" };
DateTime dt = DateTime.ParseExact(t.Text, formats, new CultureInfo("en-US"), DateTimeStyles.None);
t.Text = dt.ToString("hh:mmtt").ToLower();
And it replaces some things, like h:mm but not others like h.
Have you looked at DateTime.Parse? It accepts "08:14am", "8:14"[1] and other variants, and returns a DateTime set to 8:14 am on today's date.
[1] In the UK culture at least -- consider providing a CultureInfo parameter depending on whether you want to pay attention to the user's local format preferences, or adopt a fixed format.
EDIT I also have other replacements in mind; for example 814 goes to 08:14am, and 8 goes to 08:00am
Take a look at DateTime.ParseExact: you can provide an array of valid time formats (such as "hh:mm", "hmm", "h" etc.)
Coming at it from a completely different direction, how about using a mask on the input?
For example, there are a number of JavaScript and jQuery tools available to do this.
Using this approach retains some user control over the input, and lets the user see their input.
have you considered using a DateTimePicker? Making the user write the time looks like more of a hassle.
See e.g. http://msdn.microsoft.com/en-us/library/system.windows.forms.datetimepicker.aspx
I think regex are overkill for this. Why not simply append the "am" at the end, in case nto already added is a 2 line code in case you are working with strings in the method.
I would recommend against using regular expressions if possible (as others have said, it seems like overkill) and try using datetime formats. See here: http://msdn.microsoft.com/en-us/library/8kb3ddd4.aspx
The "HH" format tag will format the hour as a 24-hour time from 00 to 23. Traditionally, 12 hour times are not zero-padded to the left, but 24 hour times are (at least as often as I see them), probably to avoid confusion between 1800 and 0800 . Alternatively, if you don't want 24 hour times, you could probably just left-pad the hour part of the string with a zero to up to 2 digits.
EDIT:
Based on your new requirements, I'd say write a simple parser to let users input "814" meaning "08:14 AM" and make use of the time-formatting functionality for display.
Related
I assumed that ToString("yyyy/MM/dd HH:mm:ss") will force the string to be formatted with '/', but I can see that every device gets different formats. How can I force it to be saved with '/'?
Good example-
2021/10/06 18:05:53
Strange examples I see in my DB from different users-
2021-10-06 23:48:37
2021.10.12 12:41:42
2021. 10. 06 19:17:23 ('.'+ space after)
2021.10.13 19.18.16
One solution is to replace every -, . and . to /, but this only solves the strange examples I found. What if there are others?
/ in a format string means "the culture-specific date separator". If you want the literal forward-slash, quote it (and the colons, to avoid the use of a custom time separator):
ToString("yyyy'/'MM'/'dd HH':'mm':'ss")
Alternatively - and probably better - use the invariant culture. Not only will that use / as the date separator, but you won't need to worry about a culture having a different default calendar. (It'll always use the Gregorian calendar, which is presumably what you want.)
Even better, use an ISO-8601 format - you're already using a "slightly unusual for humans" format of year-first, so you might as well go the whole hog and go with the standard format for dates and times.
Sample code:
String text = dateTimeValue.ToString(
"yyyy-MM-dd'T'HH:mm:ss",
CultureInfo.InvariantCulture);
This is also the sortable standard date/time format so you can simplify the code significantly:
String text = dateTimeValue.ToString("s");
(That format always uses the invariant culture.)
That's if you really need to format the string at all, though. If you're saving it in a database, I'd advise you to:
Use an appropriate type in the database, e.g. DATETIME
Store it using a parameter (specifying the value just as a DateTime), not formatted text
If you do both of these, you'll avoid oddities like this.
Another solution that I can think of is creating a new function that creates a date
DateTime date= DateTime.UtcNow;
And extracting manually and splitting the date to a few strings (year,month,day,hour,month,seconds)
string year = date.Year.ToString(); string month = date.Month.ToString();...
and building a string out of it in the right format,
string newDate= year + "/" + month + "/" + day + " "+ hour+":"+ minute+ ":"+seconds;
that way I can be sure it's always one format that I'll decide on
How about storing the date as a number, eg unix time - DateTimeOffset.UtcNow.ToUnixTimeSeconds() or (DateTime.UtcNow - DateTime.UnixEpoch).TotalSeconds - it's a lot simpler and cheaper to store a number than a string
Also wanted to point out that the only date I've
seen you store so far is UtcNow (as written in your answer) - fire base does appear to have a solution for that in that you can send ServerValue.TIMESTAMP and it will cause fb to store the unix time as the server sees it.
My take away from this (never used fb) is that that's how they store dates so perhaps it makes sense to follow :)
I'm modifying a globalized web application which uses stored CultureInfo for each logged in user.
The client would like time data entry to be localized. Displaying is not a problem as the formatting is already available. However I need to detect if the current cultureinfo is for 24 hour time or am/pm so I can display the correct input boxes (not just a textfield).
My initial idea was to check the DateTimeInfo property of CultureInfo and see if the ShortTimePattern contained a capital H or a lower case h but this didn't feel robust enough for me.
Is there a better way? I've read the class properties of both but unless I'm missing something, I can't see any existing methods or properties.
I don't think there is a better way to obtain that information. The time pattern for a culture could contain anything (a user could even create a custom culture where the ShortTimePattern is "\hello" and then DateTime.ToString() would return "hello" for any time). In that case how could the framework determine if that CultureInfo is in 24-hour or 12-hour format?
So a "normal" DateTimeFormatInfo.ShortTimePattern will necessarily contain either a 'h' or a 'H', otherwise the hour will not be displayed. I think you can follow your initial idea and check for that. You can also check that the 'h' or 'H' is not escaped with a \ like in my "\hello" example because that would not represent the hour :)
Checking for 'H'/'h' seems more robust than checking for the AM/PM Designator.
A good example is en-gb:
The time format string is HH:mm and the AM/PM designators are set to AM/PM
Windows will display the time in 24h format!
This seems to be an inconsistent definition but checking for 'H' fixed my bug.
The most robust way is to check if DateTimeFormatInfo.AMDesignator is an empty string.
if (DateTimeFormatInfo.CurrentInfo.AMDesignator == "")
//24hour format
else
//12hour format
I was looking at a code in an application (Someone else wrote it),on some cases it worked fine and on some cases it gave exceptions,it was actually converting strings in datetime,here is the code
//5000 is the year,but what about "1" is it month or day ?,if its month
//then what about the day ?
DateTime time = DateTime.Parse("1.5000");//1.5000 doesn't looks a date to me ?
time.ToString();//returns "1/1/5000 12:00:00 AM"
//where as if I give this string to DateTime.Parse();
time = DateTime.Parse("2341.70");
//FormatException was unhandled
//String was not recognized as a valid DateTime.
A Confusing thought
How does this string "3.5000" (it matches the 1.5000 pattern) evaluates , does this means 3-3-5000 or 1-3-5000 ,the format is ambiguous its unclear and confusing !
My questions are,
What kind of formats can DateTime.Parse expects ?
Whats happening in the code above ?
Suggestions to improve the code ?
Many people have commented on the possible reasons for the parse that you have seen being successful but your question seems to have several separate parts...
1. What kind of formats can DateTime.Parse expects ?
DateTime.Parse has been written to be as inclusive as possible. Pretty much anything that it can find someway to make into a DateTime it will do its best to do so which means in addition to the usual familiar yyyy-MM-dd type formats more strange ones like M.yyyy or yyyy.M and so on.
2. Whats happening in the code above ?
That is very complicated because the DateTime.Parse method is itself very complicated. You can probably fidn the source code out there somewhere but the complexity made it very hard for me to follow. Without being able to give precise details I'm going to answer this the same as above. What is happening is that the framework is trying its best to give you a date back and not throw an exception. The date it gives is the best guess as to what you meant.
3. Suggestions to improve the code ?
It sounds like if you are getting parse exceptions that you are passing dates in formats that are unexpected. Without knowing what those inputs are its hard to say. Two things could improve your code though. Making sure a single consistent date format is used and then using DateTime.ParseExact to ensure that it conforms to the right format. You will remove all ambiguity this way but you will sacrifice flexibility.
The second option is to use DateTime.TryParse. This will attempt to parse your date and then return a boolean saying whether it succeeded or not. If successful the date parse will be returned in a ref parameter. This won't make your code any better at recognising unknown date formats but will let your code know when such an unparsable format crops up and you can deal with it (eg by providing user feedback reporting the wrong format and suggesting a correct one, or just by logging it or something else).
What the best method is depends mostly on where your input is coming from. If it is user input then I'd go with the second option. If it is automated input then you probably want to make sure your input is standardized and then use the first option. Of course circumstances always vary so this is not a hard and fast rule. :)
In regards to "2. Whats happening in the code above ?":
In some cultures, the date separator is a dot instead of a slash. So for example 13.12.2013 is a valid date (2013-12-13) in the format "dd.MM.yyyy". Now by whatever design choice, the day part in this example is not mandatory and if left out, is automatically filled with 1. So parsing 12.2013 would result in 2013-12-01. And therefore it's easy to see how 1.5000 would become 5000-01-01. 2341.70 can not be parsed, because 2341 is not a valid month. - So in this case 1.5000 is a "valid" date in the format M.yyyy.
I use asp.net 4 and c#.
I need to use a WebControl of type Validation namely RegularExpressionValidator to detect data inputed in a TextBox that IS NOT in format yyyy-MM-dd (String).
Any idea how to write the RegEx to apply ot this control?
Thanks
Here's one possible regex:
^\d{4}-((0\d)|(1[012]))-(([012]\d)|3[01])$
Note: this will prevent months >12 and days >31, but won't check specific months for length (ie it won't block 30th Feb or 31st Apr). You could write a regex to do that, but it would be quite lengthy, and 29th Feb is always going to give you problems in regex.
I'd say if you need that kind of fine-grained validation, you're better off parsing the date with a date library; regex isn't the tool for you. This regex should be sufficient for basic pre-validation though.
I've also gone lenient on the year; just checking that it's four digits. But if you want some sort of sanity check (ie within certain bounds), it shouldn't be too hard to add. Foe example, if you want to match only dates in the this century, you would replace the \d{4} at the beginning of the regex with 20\d{2}. Again, trying to validate a date with excessive accuracy in regex is going to be difficult and you should use a date parser, but you can get basic century-level matching quite easily to prevent the user entering anything really silly.
Finally, I've put ^ and $ to tie off the ends of the string so it can't match if the user enters a valid date and extra characters as well. (You may want to add a string length validator for this as well).
Hope that helps.
Spudley's answer above allows 00 for day and month.
I fixed it :
^\d{4}-((0[1-9])|(1[012]))-((0[1-9]|[12]\d)|3[01])$
Note: neither of these expressions check for days in a month that are invalid, e.g. 04/31, 06/31 or 02/29 on non-leap years.
Regular expression \d\d\d\d-\d\d-\d\d should do the trick.
I would like to add a little change in Spudley's answer:
^\d{4}$|^\d{4}-((0?\d)|(1[012]))-(((0?|[12])\d)|3[01])$
so you can use date like 2013-5-5 (month and date is not necessary the zero but can be used)
Hope it helps.
Another implementation for ISO 8601 structured dates:
^\d{4}-\d{1,2}-\d{1,2}\s\d{1,2}:\d{1,2}:\d{1,2}.?\d{0,}$
It's not quite as strict, and will accept incorrect dates, but it should validate that it follows the ISO 8601 structure even if the date is a non-existent one. It should also be fairly simple to understand for anyone with a basic Regex understanding.
If you really want to ensure the date is correct, and work with it, run DateTime.TryParse() on it.
(19|20)[0-9]{2}-(0[1-9]|1[012])-(0[1-9]|[12][0-9]|3[01])
mach result:
1999-09-12
((([0-9][0-9][0-9][1-9])|([1-9][0-9][0-9][0-9])|([0-9][1-9][0-9][0-9])|([0-9][0-9][1-9][0-9]))-((0[13578])|(1[02]))-((0[1-9])|([12][0-9])|(3[01])))|((([0-9][0-9][0-9][1-9])|([1-9][0-9][0-9][0-9])|([0-9][1-9][0-9][0-9])|([0-9][0-9][1-9][0-9]))-((0[469])|11)-((0[1-9])|([12][0-9])|(30)))|(((000[48])|([0-9]0-9)|([0-9][1-9][02468][048])|([1-9][0-9][02468][048]))-02-((0[1-9])|([12][0-9])))|((([0-9][0-9][0-9][1-9])|([1-9][0-9][0-9][0-9])|([0-9][1-9][0-9][0-9])|([0-9][0-9][1-9][0-9]))-02-((0[1-9])|([1][0-9])|([2][0-8])))
This is the regex for yyyy-MM-dd format.
You can replace - with \/ for yyyy/MM/dd...
Tested working perfect..
I'm modifying a globalized web application which uses stored CultureInfo for each logged in user.
The client would like time data entry to be localized. Displaying is not a problem as the formatting is already available. However I need to detect if the current cultureinfo is for 24 hour time or am/pm so I can display the correct input boxes (not just a textfield).
My initial idea was to check the DateTimeInfo property of CultureInfo and see if the ShortTimePattern contained a capital H or a lower case h but this didn't feel robust enough for me.
Is there a better way? I've read the class properties of both but unless I'm missing something, I can't see any existing methods or properties.
I don't think there is a better way to obtain that information. The time pattern for a culture could contain anything (a user could even create a custom culture where the ShortTimePattern is "\hello" and then DateTime.ToString() would return "hello" for any time). In that case how could the framework determine if that CultureInfo is in 24-hour or 12-hour format?
So a "normal" DateTimeFormatInfo.ShortTimePattern will necessarily contain either a 'h' or a 'H', otherwise the hour will not be displayed. I think you can follow your initial idea and check for that. You can also check that the 'h' or 'H' is not escaped with a \ like in my "\hello" example because that would not represent the hour :)
Checking for 'H'/'h' seems more robust than checking for the AM/PM Designator.
A good example is en-gb:
The time format string is HH:mm and the AM/PM designators are set to AM/PM
Windows will display the time in 24h format!
This seems to be an inconsistent definition but checking for 'H' fixed my bug.
The most robust way is to check if DateTimeFormatInfo.AMDesignator is an empty string.
if (DateTimeFormatInfo.CurrentInfo.AMDesignator == "")
//24hour format
else
//12hour format