I am trying to input a datetime value from the console. However, The TryParseExact method doesn't receive valid formats:
string startdate;
DateTime inputDate;
while (true)
{
Console.WriteLine("Input time [HH:MM TT]");
startdate = Console.ReadLine();
if (DateTime.TryParseExact(startdate, "hh:mm tt",
CultureInfo.CurrentCulture,
DateTimeStyles.None, out inputDate))
{
break;
}
}
Any suggestions?
If it is not accepting input that you think is valid then there are two possible causes of the problem:
1) The input is not what you think it is. This could be caused by copying and pasting from somewhere else that is including non-valid characters or something. IF you are manually typing the number then this is unlikely to be an issue.
2) The format you are accepting is not what you think it is. This is most likely since there are some subtleties that can bite you on this. The key think is to look up everything in http://msdn.microsoft.com/en-us/library/8kb3ddd4(v=vs.110).aspx and be aware that several elements you are using are culture dependant. You are obviously at least partially aware of cultures since you are explicitly stating you want the current culture. Without knowing what that culture is though its hard to say what the input should be.
A case in point is that in your format : doesn't mean a literal colon but the "Time Separator". To quote the MSDN page: "The ":" custom format specifier represents the time separator, which is used to differentiate hours, minutes, and seconds. The appropriate localized time separator is retrieved from the DateTimeFormatInfo.TimeSeparator property of the current or specified culture."
As you can see this means that it is not always :.
Often the best fix, especially since you are hard definining the format, is to use CultureInfo.InvariantCulture which will guarantee not to change depending on where you run the software, etc. Otherwise you should generate the string that specifies the correct input using the relevant components of your current culture object.
An example of how to write this without the white(true) loop / to try to make it easier for your users:
string startdate;
DateTime inputDate;
while (inputDate == null)
{
Console.WriteLine("Input time [HH:MM TT]");
startdate = Console.ReadLine();
if (!DateTime.TryParseExact
(
startdate, "hh:mm tt"
,CultureInfo.CurrentCulture
,DateTimeStyles.None
, out inputDate
))
{
Console.WriteLine(String.Format("'{0}' is an invalid value."));
//http://msdn.microsoft.com/en-us/library/8kb3ddd4(v=vs.110).aspx
Console.WriteLine(
String.Format("Example: The time now is '{0}'"
,DateTime.Now.ToString("hh:mm tt", CultureInfo.CurrentCulture))
);
}
}
Console.WriteLine("That's a valid time :)");
NB: your above code works in so much as given the correct input (for your user's current culture) the code exits the loop.
Related
This code returns (min time 1/1/0001 12:00:00 AM) not Date.Time.Now . Try Parse works for MM/dd/yyyy but not dd/MM/yyyy . Any suggestions
Here is code
DateTime start, end;
DateTime.TryParse(EPSDate12.Text, out start);
string TNow = DateTime.Now.ToString("dd/MM/yyyy HH:mm:ss"); // Works
// string TNow = DateTime.Now.ToString();// works but gives MM/dd/yyyy as expected
DateTime.TryParse(TNow, out end); // No. gives min time (1/1/0001 12:00:00 AM)
Use TryParseExact and supply the format string.
Also examine the return value from TryParseExact to know if it failed or not (it returns a bool)
I see "EPSDate12.Text" which i suspect may be a TextBox: If you're doing this in a UI, make life easy and use a DateTimePicker - you can set the format, the user can type into them just like a textbox, but they don't accept invalid inputs, and all you have to do is get the .Value property which gives you a DateTime
As to why your attempts to parse the string you made don't work, I think it most likely that the date format Parse is using (which is based on the culture settings of the executing thread) is not the same format as the string you prepared using your forced format. Either make sure your forced format is matched to the current culture, or use a culture that matches your forced format, or use [Try]ParseExact to force the format for parsing like you did when creating the string
See https://learn.microsoft.com/en-us/dotnet/api/system.datetime.parse?view=net-5.0#Culture for more info
The datetime value is internally the same. But, ToString() return value, depends on
the local machine culture setup.
Reference article
The default DateTime.ToString() method returns the string
representation of a date and time value using the current culture's
short date and long time pattern. The following example uses the
default DateTime.ToString() method.
For en-US culture(MM/dd/yyyy hh:mm:ss) , it will be in
7/28/2021 11:37:40 AM
If you want to see in en-GB(dd/MM/yyyy hh:mm:ss), you can apply conversion as given below:
var culture = new CultureInfo("en-GB");
MessageBox.Show($"{DateTime.Now.ToString(culture)}");
28/07/2021 11:45:09 AM
you can also specify exact custom format, in which you want to display.
MessageBox.Show($"{DateTime.Now.ToString("dd/MM/yyyy HH:mm:ss tt")}");
28/07/2021 11:45:09 AM
Thanks for suggestions . Yes DateTime.TryParse is not working and it could be format issue
This line of code.
string TNow = DateTime.Now.ToString("dd/MM/yyyy HH:mm:ss");
generates
29/07/2021 14:49:03
which looks OK but fails TryParse
In my code I need to handle two types of datetime formats. if the input date is a like 8/31/2017 12:00:00 AM I just wanna save it. But when it comes with the format like "25.11.13" I wanna convert it like this 11/25/2013 12:00:00 AM and wanna save it.
Somehow I managed my code but the problem is the "else block" is not working as expected (actually it won't work at all).
DateTime registrationDate = new DateTime();
if (DateTime.TryParse(myTable.Rows[i][6].ToString(), out registrationDate))
{
record.RegistrationDate = !string.IsNullOrEmpty(detailsTable.Rows[i][6].ToString()) ? Convert.ToDateTime(detailsTable.Rows[i][6].ToString()) : (DateTime?)null;
}
else
{
DateTime.TryParse(detailsTable.Rows[i][6].ToString(), out registrationDate);
record.RegistrationDate = registrationDate;
}
I think you have a culture issue here. "8/31/2017" is clearly in US format M/D/Y because no month has 31 days. However "25.11.13" is in another D/M/Y (possibly UK) format.
Unless your detailsTable contains the culture the value is in you are stuck here. This is because it is impossible to tell if 9/11/2001 is the 9th of November or 11th of September without further information.
DateTime.TryParse will try to use the culture of the user that is running the code. Note if it is a web site then it runs as the account the IIS Service is set to use. There is an overload of TryParse that takes another parameter that allows you to tell it which culture the supplied string is in.
If you know that all dates that have slashes '/' are in US format and all dates that have dots '.' are in UK format then you can pre-parse the string to enable you to tell TryParse the correct culture. Like this:
static DateTime Parse(string input)
{
CultureInfo ci =
CultureInfo.CreateSpecificCulture(
input.Contains(".") ?
"en-GB" :
"en-US");
DateTime result;
DateTime.TryParse(input, ci, DateTimeStyles.None, out result);
return result;
}
I'm parsing this date: "3/1/1961" with the following code:
DateTime d = DateTime.ParseExact(theStringDate, "d", lang.Culture);
I think everybody will agree with me that "3/1/1961" and "03/01/1961" are the same date. However, in the first case the code will crash and in the second it will not.
Why is C# behaving this way? Is there any way "3/1/1961" should not get interpreted correctly? How can I tell the compiler to ignore the absence of 0 before the number?
Forcing my user to write 0 before every number or using JS to force the presence of a 0 are both unacceptable solutions. What can I do?
What is the value of lang.Culture?
When the problem arised, I was testing from an italian browser so, I guess, it is "IT-it".
I am not sure how you are parsing with the current format d, it should be "d/M/yyyy"
string theStringDate = "03/01/1961";
DateTime d = DateTime.ParseExact(theStringDate, "d/M/yyyy", CultureInfo.InvariantCulture);
The format "d/M/yyyy" works for both single digit and double digits day/month.
You're using parse exact and the input string isn't in the format you specify. C# is not behaving weird, you're just misusing the method. This snippet is directly from msdn and exactly explains why you get an exception;
// Parse date-only value without leading zero in month using "d" format.
// Should throw a FormatException because standard short date pattern of
// invariant culture requires two-digit month.
dateString = "6/15/2008";
try {
result = DateTime.ParseExact(dateString, format, provider);
Console.WriteLine("{0} converts to {1}.", dateString, result.ToString());
}
catch (FormatException) {
Console.WriteLine("{0} is not in the correct format.", dateString);
}
There are several solutions available to you. Here are few off the top of my head; change your format specifier (I think replacing "d" with "g" will solve your problem in this case, you'll still get exceptions for other formats though), change DateTime.ParseExact to DateTime.Parse or DateTime.TryParse, or change your input so it's in the exact format you require.
Personally I'd recommend getting rid of ParseExact. Do you know exactly what format your date is going to be in? It seems like you don't. If you don't, why would you be using ParseExact?
I want to parse string to time, the string can be "hh:mm tt", or "hh:mmtt"
"11:00am", "11:00 am", "13:00" "5:00AM" "6:00PM" , "6:00 pm", "6:00:01 pm" etc.
I wonder how to parse it correctly. My thought is to enumerate all the formats like below.
But I feel it is awkward and there must be a better way. thanks
DateTime ret = DateTime.MinValue;
DateTime.TryParse(timeStr, CURRENT_CULTURE_FORMATPROVIDER,Style1, out ret);
if(ret == DateTime.MinValue)
{
DateTime.TryParse(timeStr,CURRENT_CULTURE_FORMATPROVIDER,Style2, out ret);
}
if(ret == DateTime.MinValue)
{
DateTime.TryParse(timeStr,CURRENT_CULTURE_FORMATPROVIDER,Style3, out ret);
}
...
return ret;
Not really an answer but not fitting to comments: reject values that are not completely clear instead of potentially guessing wrong.
While it is very tempting to guess what actual value particular string represents it is very dangerous route. The chances of guessing value wrong are higher more input "formats" you accept.
If data coming from some computer-generated source - simply rejecting unexpected data is probably best option. Consider if asking for some fixed well known culture-insensitive format works (i.e. ISO8601 optionally with timezone)
If this data coming directly from user it may be better to immediately reject the data and let user re-enter date in more precise format. If possible - simply don't let user to pick and force particular format.
If you randomly guess values incorrectly users (if they care and have to use your tool often) will learn to type values in one very particular format and have verbal instructions to only use that (like "hours two spaces colon minutes, only add PM for values in afternoon")...
Note that only some cultures (in .Net sense) have AM/PM designator, so make sure to test your code against those too.
DateTime.TryParse seems to be working for your problem. Have a look
string myTime = "5:00AM";
DateTime dt = DateTime.Now;
DateTime.TryParse(ss, out dt);
I have a DateTime object and I want to output the hour, minute, second, and fractional second as a string that is localized for the current culture.
There are two issues with this.
First issue is there is no standard DateTime format that will show the fractional seconds. I essentially want to know how to get the long time DateTime format but with fractional seconds.
I could of course get DateTimeFormatInfo.LongTimePattern and append ".fff" to it and pass it to the DateTime.ToString(), but some of the culture specific formats, US specifically, end with AM/PM. So it isn't that simple.
The second issue is that DateTime.ToString() does not appear to localize the number decimal separator. If I decided to just force each culture to use a hard coded custom time format it still will not create a localized string as the number decimal separator will not be culture specific.
To complicate matters further, some cultures have date time formats that use periods as part of their formatting. This makes it difficult to put a placeholder, for example the period and replace it with a culture specific decimal separator.
For now I have resorted to this workaround:
string format = string.Format("HH:mm:ss{0}fff",
CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator);
string time = DateTime.Now.ToString(format);
Which I think should work for every culture that doesn't have the same decimal separator as the time separator, but that is an assumption.
Of Note: While it would be nice to have a solution to both issues, for my specific application I am more interested in localizing a custom date time format with fractional seconds than using a standard date time format.
First issue is there is no standard DateTime format that will show the fractional seconds. I essentially want to know how to get the long time DateTime format but with fractional seconds.
You might consider taking the long format and just replacing ":ss" with ":ss.fff", possibly using the culture-specific decimal separator:
string longPattern = culture.DateTimeFormat.LongTimePattern;
if (!longPattern.Contains(":ss"))
{
// ???? Throw an exception? Test this with all system cultures, but be aware
// that you might see custom ones...
}
// Only do it if the long pattern doesn't already contain .fff... although if
// it does, you might want to replace it using the culture's decimal separator...
if (!longPattern.Contains(".fff"))
{
longPattern = longPattern.Replace(":ss",
":ss" + culture.NumberFormat.DecimalSeparator + "fff");
}
string timeText = time.ToString(longPattern, culture);
To complicate matters further, some cultures have date time formats that use periods as part of their formatting. This makes it difficult to put a placeholder, for example the period and replace it with a culture specific decimal separator. Other than that though, it should end up putting the value in the right place. Do you definitely always want three digits though, even if the value is an exact second (or half a second, etc)? Use .FFF if not.
I suspect that's why the culture-specific decimal separator isn't used. I've found it odd myself - indeed, I've made Noda Time behave the same way, even though I'm not convinced it's right.
Ultimately, a lot of issues like this are fundamentally problematic: if a culture has no fixed way of representing "a time with fractional seconds" and you've got to represent fractional seconds, then the best you're going to be able to do is a bit of a kludge.
I think this will give you something close to what you require
var now = DateTime.Now;
var seconds = now.TimeOfDay.TotalSeconds % 60;
var timeText = string.Format(CultureInfo.GetCultureInfo("fr-FR"),
"{0:d} {0:hh:mm:}{1:00.000}", now, seconds);
or just use
var timeText = string.Format(CultureInfo.CurrentCulture,
"{0:d} {0:hh:mm:}{1:00.000}", now, seconds);
For example
fr-FR: 20/03/2012 10:20:10,088
en-GB: 20/03/2012 10:21:08.724
en-US: 3/20/2012 10:21:24.470
Generally I change the current culture and I do the operation I need.
System.Globalization.CultureInfo before = System.Threading.Thread.CurrentThread.CurrentCulture;
try
{
System.Threading.Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo("en-US");
string timestr = DateTime.Now.ToString();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
finally
{
System.Threading.Thread.CurrentThread.CurrentUICulture = before;
}