I am using Datetime.TryParse method to check the valid datetime. the input date string would be any string data. but is returning false as the specify date in invalid.
DateTime fromDateValue;
if (DateTime.TryParse("15/07/2012", out fromDateValue))
{
//do for valid date
}
else
{
//do for in-valid date
}
Edit: I missed. I need to check the valid date with time as "15/07/2012 12:00:00".
Any suggestions are welcome.
You could use the TryParseExact method which allows you to pass a collection of possible formats that you want to support. The TryParse method is culture dependent so be very careful if you decide to use it.
So for example:
DateTime fromDateValue;
string s = "15/07/2012";
var formats = new[] { "dd/MM/yyyy", "yyyy-MM-dd" };
if (DateTime.TryParseExact(s, formats, CultureInfo.InvariantCulture, DateTimeStyles.None, out fromDateValue))
{
// do for valid date
}
else
{
// do for invalid date
}
You should be using TryParseExact as you seem to have the format fixed in your case.
Something like can also work for you
DateTime.ParseExact([yourdatehere],
new[] { "dd/MM/yyyy", "dd/M/yyyy" },
CultureInfo.InvariantCulture,
DateTimeStyles.None);
As the others said, you can use TryParseExact.
For more informations and the use with the time, you can check the MSDN Documentation
Related
I am suppose to let the user enter a DateTime format, but I need to validate it to check if it is acceptable. The user might enter "yyyy-MM-dd" and it would be fine, but they can also enter "MM/yyyyMM/ddd" or any other combination. Is there a way to validate this?
Are you looking for something like this?
DateTime expectedDate;
if (!DateTime.TryParse("07/27/2012", out expectedDate))
{
Console.Write("Luke I am not your datetime.... NOOO!!!!!!!!!!!!!!");
}
If your user knows the exact format(s) needed...
string[] formats = { "MM/dd/yyyy", "M/d/yyyy", "M/dd/yyyy", "MM/d/yyyy" };
DateTime expectedDate;
if (!DateTime.TryParseExact("07/27/2012", formats, new CultureInfo("en-US"),
DateTimeStyles.None, out expectedDate))
{
Console.Write("Thank you Mario, but the DateTime is in another format.");
}
I don't know of any way to actually validate the format they enter since sometimes you want to intentionally include characters that translate into anything. One thing you might consider is allowing the user to self validate by showing a preview of what their entered format translates into.
I assume you want to know if the specified format string is valid...
For this you could round-trip it:
private bool IsValidDateFormat(string dateFormat)
{
try
{
String dts=DateTime.Now.ToString(dateFormat, CultureInfo.InvariantCulture);
DateTime.ParseExact(dts, dateFormat, CultureInfo.InvariantCulture);
return true;
}
catch (Exception)
{
return false;
}
}
Unless I am remembering incorrectly, the only invalid DateTime format strings are one character long. You can assume any 2 or more character DateTime format string is valid.
DateTime.ParseExact("qq", "qq", null) == DateTime.Today
DateTime.ParseExact("myy", "501", null) == "05/01/2001"
Standard (1 character)
Custom (>1 character)
For reference, allowed single character strings as formats:
d,D,f,F,g,G,m,M,o,O,r,R,s,T,u,U,y,Y
Any other character, such as q, by itself is invalid. All other strings will be successfully parsed as formatting strings.
You don't talk about your validation strategy. Anyway you should use something involving regular expressions and than apply allowed patterns. This would help against the formal validity .. then you have to take care about the actual contents and be sure the values are correct according as month, day and year.
Anyway several people suggested to use the DateTime.TryParse() method to let the substrate take care for you. But you'll have to specify the format anyway! so there's no magic! you would fall in ambiguity otherwise
This works for me-
try
{
String formattedDate = DateTime.Now.ToString(dateFormat);
DateTime.Parse(formattedDate);
return true;
}
catch (Exception)
{
return false;
}
static private bool IsValidDateFormat(string dateFormat)
{
try
{
DateTime pastDate = DateTime.Now.Date.Subtract(new TimeSpan(10, 0, 0, 0, 0));
string pastDateString = pastDate.ToString(dateFormat, CultureInfo.InvariantCulture);
DateTime parsedDate = DateTime.ParseExact(pastDateString, dateFormat, CultureInfo.InvariantCulture);
if (parsedDate.Date.CompareTo(pastDate.Date) ==0)
{
return true;
}
return false;
}
catch
{
return false;
}
}
I do use this code - it is a modification of shapiro yaacov posting.
It looks as "DateTime.ParseExact" does not throw an exception when using an invalid dateformat string - it just returns "DateTime.Now".
My approach is to convert a date in the past to string and then check if this is returned by ParseExact()
The answer by ZipXap accepts any format that doesn't throw an exception, yet something like "aaaa" will pass that validation and give the current date at midnight ("26-Apr-22 00:00:00" when writing this).
A better aproach is to use the DateTimeStyles.NoCurrentDateDefault option and compare the result to default:
using System.Globalization;
var format = "aaaaa";
try {
var dt = DateTime.ParseExact(
DateTime.Now.ToString(format, CultureInfo.InvariantCulture),
format,
CultureInfo.InvariantCulture,
DateTimeStyles.NoCurrentDateDefault);
return dt != default;
} catch {
return false;
}
/*
"aaaaa" -> false
"h" -> false
"hh" -> true
"fff" -> true
"gg" -> false
"yyyy gg" -> true
"'timezone: 'K" -> false
"zzz" -> false
*/
My solution was to mark the input-field as read-only and allow users to change the value only by jqueryui datepicker.
It is intuitive. You can specify your preferred format and need only to validate this one format.
Otherwise you may get really in trouble. What are you going to do with "02/03/2020" in USA you interpret it as the third of February, but for south america it is definitely the second of March. And there are a lot of other Date formats around the globe.
I have date and time in a string formatted like that one:
"2011-03-21 13:26" //year-month-day hour:minute
How can I parse it to System.DateTime?
I want to use functions like DateTime.Parse() or DateTime.ParseExact() if possible, to be able to specify the format of the date manually.
DateTime.Parse() will try figure out the format of the given date, and it usually does a good job. If you can guarantee dates will always be in a given format then you can use ParseExact():
string s = "2011-03-21 13:26";
DateTime dt =
DateTime.ParseExact(s, "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture);
(But note that it is usually safer to use one of the TryParse methods in case a date is not in the expected format)
Make sure to check Custom Date and Time Format Strings when constructing format string, especially pay attention to number of letters and case (i.e. "MM" and "mm" mean very different things).
Another useful resource for C# format strings is String Formatting in C#
As I am explaining later, I would always favor the TryParse and TryParseExact methods. Because they are a bit bulky to use, I have written an extension method which makes parsing much easier:
var dtStr = "2011-03-21 13:26";
DateTime? dt = dtStr.ToDate("yyyy-MM-dd HH:mm");
Or more simply, if you want to use the date patterns of your current culture implicitly, you can use it like:
DateTime? dt = dtStr.ToDate();
In that case no specific pattern need to be specified.
Unlike Parse, ParseExact etc. it does not throw an exception, and allows you to check via
if (dt.HasValue) { // continue processing } else { // do error handling }
whether the conversion was successful (in this case dt has a value you can access via dt.Value) or not (in this case, it is null).
That even allows to use elegant shortcuts like the "Elvis"-operator ?., for example:
int? year = dtStr?.ToDate("yyyy-MM-dd HH:mm")?.Year;
Here you can also use year.HasValue to check if the conversion succeeded, and if it did not succeed then year will contain null, otherwise the year portion of the date. There is no exception thrown if the conversion failed.
Solution: The .ToDate() extension method
Try it in .NetFiddle
public static class Extensions
{
/// Extension method parsing a date string to a DateTime? <para/>
/// <summary>
/// </summary>
/// <param name="dateTimeStr">The date string to parse</param>
/// <param name="dateFmt">dateFmt is optional and allows to pass
/// a parsing pattern array or one or more patterns passed
/// as string parameters</param>
/// <returns>Parsed DateTime or null</returns>
public static DateTime? ToDate(this string dateTimeStr, params string[] dateFmt)
{
// example: var dt = "2011-03-21 13:26".ToDate(new string[]{"yyyy-MM-dd HH:mm",
// "M/d/yyyy h:mm:ss tt"});
// or simpler:
// var dt = "2011-03-21 13:26".ToDate("yyyy-MM-dd HH:mm", "M/d/yyyy h:mm:ss tt");
const DateTimeStyles style = DateTimeStyles.AllowWhiteSpaces;
if (dateFmt == null)
{
var dateInfo = System.Threading.Thread.CurrentThread.CurrentCulture.DateTimeFormat;
dateFmt=dateInfo.GetAllDateTimePatterns();
}
var result = DateTime.TryParseExact(dateTimeStr, dateFmt, CultureInfo.InvariantCulture,
style, out var dt) ? dt : null as DateTime?;
return result;
}
}
Some information about the code
You might wonder, why I have used InvariantCulture calling TryParseExact: This is to force the function to treat format patterns always the same way (otherwise for example "." could be interpreted as decimal separator in English while it is a group separator or a date separator in German). Recall we have already queried the culture based format strings a few lines before so that is okay here.
Update: .ToDate() (without parameters) now defaults to all common date/time patterns of the thread's current culture.
Note that we need the result and dt together, because TryParseExact does not allow to use DateTime?, which we intend to return.
In C# Version 7 you could simplify the ToDate function a bit as follows:
// in C#7 only: "DateTime dt;" - no longer required, declare implicitly
if (DateTime.TryParseExact(dateTimeStr, dateFmt,
CultureInfo.InvariantCulture, style, out var dt)) result = dt;
or, if you like it even shorter:
// in C#7 only: Declaration of result as a "one-liner" ;-)
var result = DateTime.TryParseExact(dateTimeStr, dateFmt, CultureInfo.InvariantCulture,
style, out var dt) ? dt : null as DateTime?;
in which case you don't need the two declarations DateTime? result = null; and DateTime dt; at all - you can do it in one line of code.
(It would also be allowed to write out DateTime dt instead of out var dt if you prefer that).
The old style of C# would have required it the following way (I removed that from the code above):
// DateTime? result = null;
// DateTime dt;
// if (DateTime.TryParseExact(dateTimeStr, dateFmt,
// CultureInfo.InvariantCulture, style, out dt)) result = dt;
I have simplified the code further by using the params keyword: Now you don't need the 2nd overloaded method any more.
Example of usage
var dtStr="2011-03-21 13:26";
var dt=dtStr.ToDate("yyyy-MM-dd HH:mm");
if (dt.HasValue)
{
Console.WriteLine("Successful!");
// ... dt.Value now contains the converted DateTime ...
}
else
{
Console.WriteLine("Invalid date format!");
}
As you can see, this example just queries dt.HasValue to see if the conversion was successful or not. As an extra bonus, TryParseExact allows to specify strict DateTimeStyles so you know exactly whether a proper date/time string has been passed or not.
More Examples of usage
The overloaded function allows you to pass an array of valid formats used for parsing/converting dates as shown here as well (TryParseExact directly supports this), e.g.
string[] dateFmt = {"M/d/yyyy h:mm:ss tt", "M/d/yyyy h:mm tt",
"MM/dd/yyyy hh:mm:ss", "M/d/yyyy h:mm:ss",
"M/d/yyyy hh:mm tt", "M/d/yyyy hh tt",
"M/d/yyyy h:mm", "M/d/yyyy h:mm",
"MM/dd/yyyy hh:mm", "M/dd/yyyy hh:mm"};
var dtStr="5/1/2009 6:32 PM";
var dt=dtStr.ToDate(dateFmt);
If you have only a few template patterns, you can also write:
var dateStr = "2011-03-21 13:26";
var dt = dateStr.ToDate("yyyy-MM-dd HH:mm", "M/d/yyyy h:mm:ss tt");
Advanced examples
You can use the ?? operator to default to a fail-safe format, e.g.
var dtStr = "2017-12-30 11:37:00";
var dt = (dtStr.ToDate()) ?? dtStr.ToDate("yyyy-MM-dd HH:mm:ss");
In this case, the .ToDate() would use common local culture date formats, and if all these failed, it would try to use the ISO standard format "yyyy-MM-dd HH:mm:ss" as a fallback. This way, the extension function allows to "chain" different fallback formats easily.
You can even use the extension in LINQ, try this out (it's in the .NetFiddle above):
var strDateArray = new[] { "15-01-2019", "15.01.2021" };
var patterns=new[] { "dd-MM-yyyy", "dd.MM.yyyy" };
var dtRange = strDateArray.Select(s => s.ToDate(patterns));
dtRange.Dump();
which will convert the dates in the array on the fly by using the patterns and dump them to the console.
Some background about TryParseExact
Finally, Here are some comments about the background (i.e. the reason why I have written it this way):
I am preferring TryParseExact in this extension method, because you avoid exception handling - you can read in Eric Lippert's article about exceptions why you should use TryParse rather than Parse, I quote him about that topic:2)
This unfortunate design decision1) [annotation: to
let the Parse method throw an exception] was so vexing that of course
the frameworks team implemented TryParse shortly thereafter which does the right thing.
It does, but TryParse and TryParseExact both are still a lot less than comfortable to use: They force you to use an uninitialized variable as an out parameter which must not be nullable and while you're converting you need to evaluate the boolean return value - either you have to use an ifstatement immediately or you have to store the return value in an additional boolean variable so you're able to do the check later. And you can't just use the target variable without knowing if the conversion was successful or not.
In most cases you just want to know whether the conversion was successful or not (and of course the value if it was successful), so a nullable target variable which keeps all the information would be desirable and much more elegant - because the entire information is just stored in one place: That is consistent and easy to use, and much less error-prone.
The extension method I have written does exactly that (it also shows you what kind of code you would have to write every time if you're not going to use it).
I believe the benefit of .ToDate(strDateFormat) is that it looks simple and clean - as simple as the original DateTime.Parse was supposed to be - but with the ability to check if the conversion was successful, and without throwing exceptions.
1) What is meant here is that exception handling (i.e. a try { ... } catch(Exception ex) { ...} block) - which is necessary when you're using Parse because it will throw an exception if an invalid string is parsed - is not only unnecessary in this case but also annoying, and complicating your code. TryParse avoids all this as the code sample I've provided is showing.
2) Eric Lippert is a famous StackOverflow fellow and was working at Microsoft as principal developer on the C# compiler team for a couple of years.
var dateStr = #"2011-03-21 13:26";
var dateTime = DateTime.ParseExact(dateStr, "yyyy-MM-dd HH:mm", CultureInfo.CurrentCulture);
Check out this link for other format strings!
DateTime.Parse() should work fine for that string format. Reference:
http://msdn.microsoft.com/en-us/library/1k1skd40.aspx#Y1240
Is it throwing a FormatException for you?
Put the value of a human-readable string into a .NET DateTime with code like this:
DateTime.ParseExact("April 16, 2011 4:27 pm", "MMMM d, yyyy h:mm tt", null);
You can also use XmlConvert.ToDateString
var dateStr = "2011-03-21 13:26";
var parsedDate = XmlConvert.ToDateTime(dateStr, "yyyy-MM-dd hh:mm");
It is good to specify the date kind, the code is:
var anotherParsedDate = DateTime.ParseExact(dateStr, "yyyy-MM-dd hh:mm", CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal);
More details on different parsing options http://amir-shenodua.blogspot.ie/2017/06/datetime-parsing-in-net.html
The simple and straightforward answer -->
using System;
namespace DemoApp.App
{
public class TestClassDate
{
public static DateTime GetDate(string string_date)
{
DateTime dateValue;
if (DateTime.TryParse(string_date, out dateValue))
Console.WriteLine("Converted '{0}' to {1}.", string_date, dateValue);
else
Console.WriteLine("Unable to convert '{0}' to a date.", string_date);
return dateValue;
}
public static void Main()
{
string inString = "05/01/2009 06:32:00";
GetDate(inString);
}
}
}
/**
* Output:
* Converted '05/01/2009 06:32:00' to 5/1/2009 6:32:00 AM.
* */
Try the following code
Month = Date = DateTime.Now.Month.ToString();
Year = DateTime.Now.Year.ToString();
ViewBag.Today = System.Globalization.CultureInfo.InvariantCulture.DateTimeFormat.GetMonthName(Int32.Parse(Month)) + Year;
DateTime.ParseExact(DateTime, Format, DateTimeFormatInfo.InvariantInfo, DateTimeStyles.AllowLeadingWhite | DateTimeStyles.AllowTrailingWhite)
for example:
DateTime.ParseExact("2011-03-21 13:26", "yyyy-MM-dd hh:mm", DateTimeFormatInfo.InvariantInfo, DateTimeStyles.AllowLeadingWhite | DateTimeStyles.AllowTrailingWhite);
Is there a way, a good way, to test if a string than I want to transform in DateTime is dd/MM/yyyy or MM/dd/yyyy ?
Thanks,
No, because it could be both. Is 11/10/2010 November 10th or October 11th?
Yes, in some cases (if one number is above 12) it will be unambiguous - but I think it's better to force one format or the other. If you just treat anything which can be done as MM/dd/yyyy that way, and move on to dd/MM/yyyy if it fails (or the other way round) then you'll get some very surprised users.
If this is part of a web application or something similar, I would try to make it completely unambiguous by using month names instead of numbers where possible.
No, but you could try both when parsing:
DateTime result;
if (DateTime.TryParseExact(
"05/10/2010",
new[] { "MM/dd/yyyy", "dd/MM/yyyy" },
CultureInfo.InvariantCulture,
DateTimeStyles.None,
out result)
)
{
// successfully parsed date => use the result variable
}
This problem will exist until all accepts and uses the ISO way. I'm a Swedish programmer working a lot with American and English clients and it's surprisingly hard to get these clients to use the standardized date format.
ISO 8601 - Use it!
Take a look at DateTime.ParseExact and DateTime.TryParseExact.
string date1 = "24/12/2010";
CultureInfo provider = CultureInfo.InvariantCulture;
DateTime dt1 = new DateTime(1, 1, 1);
bool dt1Valid = false;
try
{
dt1 = DateTime.ParseExact(date1, "dd/MM/yyyy", provider);
dt1Valid = true;
}
catch
{
dt1Valid = false;
}
I want to convert text to datetime but having error.My text box value is in format dd/MM/yyyy
String was not recognized as a valid DateTime.
myFtMaster.GENTRTYDATEFROM =Convert.ToDateTime(txtTreatyPeriodfrom.Text.ToString());
My business object 'gentrtydatefrom' datatype is DateTime. Also what is the best way to avoid these type of errors without using a Try catch block.
You either specify a culture that uses that specific format:
myFtMaster.GENTRTYDATEFROM = Convert.ToDateTime(
txtTreatyPeriodfrom.Text, CultureInfo.GetCulture("en-GB")
);
or use the ParseExact method:
myFtMaster.GENTRTYDATEFROM = DateTime.ParseExact(
txtTreatyPeriodfrom.Text, "dd/MM/yyyy", CultureInfo.Invariant
);
The ParseExact method only accepts that specific format, while the Convert.ToDateTime method still allows some variations on the format, and also accepts some other date formats.
To catch illegal input, you can use the TryParseExact method:
DateTime d;
if (DateTime.TryParseExact(txtTreatyPeriodfrom.Text, "dd/MM/yyyy", CultureInfo.Invariant, DateTimeStyles.None, out d)) {
myFtMaster.GENTRTYDATEFROM = d;
} else {
// communcate the failure to the user
}
Use something like the following instead:
DateTime date = DateTime.MinValue;
DateTime.TryParse(txtTreatyPeriodfrom.Text, out date);
TryParse is similar to DateTime.Parse() but it does not throw an exception if the conversion fails.
If you want to use the en-CA specific culture use the following:
DateTime.TryParse(txtTreatyPeriodfrom.Text, new CultureInfo("en-CA"),
DateTimeStyles.AllowWhiteSpaces, out date);
Then obviously deal with those dates that fail to parse.
Ensuring the user is prompted on the format will obviously reduce mistakes.
Have a look at
DateTime.TryParse(String value, out DateTime, [culture settings])
I have a string 12012009 input by the user in ASP.NET MVC application. I wanted to convert this to a DateTime.
But if I do DateTime.TryParse("12012009", out outDateTime); it returns a false.
So I tried to convert 12012009 to 12/01/2009 and then do
DateTime.TryParse("12/01/2009", out outDateTime); which will work
But I don't find any straight forward method to convert string 12012009 to string "12/01/2009". Any ideas?
First, you need to decide if your input is in day-month-year or month-day-year format.
Then you can use DateTime.TryParseExact and explicitly specify the format of the input string:
DateTime.TryParseExact("12012009",
"ddMMyyyy",
CultureInfo.InvariantCulture,
DateTimeStyles.None,
out convertedDate)
See also: Custom Date and Time Format Strings
You can use the DateTime.TryParseExact and pass in the exact format string:
DateTime dateValue = DateTime.Now;
if (DateTime.TryParseExact("12012009", "ddMMyyyy", CultureInfo.InvariantCulture, DateTimeStyles.None, out dateValue)))
{
// Date now in dateValue
}
If you want to use that format you will most likely need to specify the format to the parser. Check the System.IFormatProvider documentation as well as the System.DateTime documentation for methods that take an IFormatProvider.
DateTime yourDate =
DateTime.ParseExact(yourString, "ddMMyyyy", Culture.InvariantCulture);