I have problem with the DateTime data type. Through a textbox I want to add person dateofbirth. As there is no date datatype in C# i am forced to use the DateTime datatype, but while converting TxtDateofBirth to DateTime i am getting an error, "String was not recognized as a valid DateTime." Here is my conversion the code. I kept this code in add event.
DateTime dateofbirth = Convert.ToDateTime(TxtDateOfBirth.Text);
What should I do?
Thanks,
Masum
Use DateTime.ParseExact with a format string which only specifies the date part.
Alternatively, as this is user input, use DateTime.TryParseExact so you don't need to catch an exception if the user has entered a bad date:
using System;
class Test
{
static void Main()
{
TestParsing("24/10/2009");
TestParsing("flibble");
}
static void TestParsing(string text)
{
DateTime dt;
if (DateTime.TryParseExact(text, "d", null, 0, out dt))
{
Console.WriteLine("Parsed to {0}", dt);
}
else
{
Console.WriteLine("Bad date");
}
}
}
Note that the format string "d" means "short date format" (see the "standard date and time form at strings" and "custom date and time format strings" pages in MSDN). "null" means "use the current culture" - so the above works for me in the UK, but you'd need to make the string "10/24/2009" in the US. You could specify a particular culture if you don't want to use the thread's current default. 0 means the default date and time style. Look at the MSDN page for more information.
Alternatively , use a mask so that users can only enter valid dates. (See the c# section under examples on the link given)
There is hardly anything one could add to Jon's answers, but in this case I'd like to make a point:
Try to understand that your problem is not because of the DateTime datatype but because your date string does not match the expected format (based on regional settings/thread culture) that the DateTime constructor.
You say that you are "forced" to use the DateTime datatype. You should keep in mind that Dates should always be treated as Dates. I've seen too many developers fall into the trap of using dates as strings (and performing split/search operations) rather than using DateTime because they feel that the latter is too complicated.
Related
I was trying to validate a date read from app.config file using DateTime.TryParse() method. However, it returned true when the input was "12/05/201". This was actually a typo, and should have been, "12/05/2018". When I stepped through the code it automatically converted the date to "12/05/0201" and returned true. However when I used DateTime.TryParseExact(), it correctly returned false for the above input. So, should we always use DateTime.TryParseExact()? I am little confused because earlier I used use DateTime.TryParse() whenever I had to validate a date string! Both the code is given below:
Boolean isValidStartDate = DateTime.TryParse(startDate, out DateTime startDateVerified);
CultureInfo enUS = new CultureInfo("en-US");
Boolean isValidStartDate = DateTime.TryParseExact(startDate,"MM/dd/yyyy",enUS, DateTimeStyles.None, out DateTime startDateVerified);
Thanks
The year 201 being invalid is business logic - if you want to have logical safeguards on your imported data (and you should), do them explicitly. With C# you can easily add an extension method to DateTime if you want, something like
public static DateTime ParseDateWithSanity(this DateTime, string date)
{
dt = DateTime.Parse(date);
if dt.Year < 1900
{
throw BadInputException()
}
}
Best way to Validate date depends upon the use case and input data source and its formate
DateTime.TryParse is parsed using formatting information in the current DateTimeFormatInfo object so let's say if you use TryParse "12/05/201" it will return the parsed data according to your current culture settings. Which is "12/05/0201" ie in date format "MM/DD/YYYY"
Its always good practice to specify date formate and culture variance while parsing date and use TryParseExact instead of TryParse
(Note: To know about current culture settings you can look for a member of classes CultureInfo.DefaultThreadCurrentCulture and CultureInfo.DefaultThreadCurrentUICulture)
I'm trying to convert some DateTime values to string format yyyy-MM-dd. The problem is i only need the date but in my case model.StartDate contains both date and time. When declaring model.StartDate as string "start" looks like this: 4/1/2014 12:00:00 AM. I get this error when trying to parse:
System.FormatException was unhandled by user code Message=String was
not recognized as a valid DateTime.
My best guess is that the error occurs because string contains both Date and Time but i could be wrong. If i explore model.StartDate further i can also find Day, DayOfTheWeek etc. Is this the right approach? I just want to convert model.StartDate to string "start" with format yyyy-MM-dd.
Heres my code:
string start = model.StartDate.ToString();
model.StartDate = DateTime.ParseExact(start, "yyyy-MM-dd", CultureInfo.InvariantCulture);
string end = model.EndDate.ToString();
model.EndDate = DateTime.ParseExact(end, "yyyy-MM-dd", CultureInfo.InvariantCulture);
Dunno what the problem is, might be that start contains time? I have no idea.
The model.StartDate and model.EndDate are DateTime properties from the view model:
[NopResourceDisplayName("Admin.GAStatistics.GAStatistics.StartDate")]
[UIHint("DateNullable")]
public DateTime? StartDate { get; set; }
[NopResourceDisplayName("Admin.GAStatistics.GAStatistics.EndDate")]
[UIHint("DateNullable")]
public DateTime? EndDate { get; set; }
EDIT:
Iv'e uploaded a image here showing the actual output i'm getting in the debugger:
https://imageshack.com/i/1n51u2p
Thank you
You are converting the dates to string but you don't specify the format. Try
string start = model.StartDate.ToString("yyyy-MM-dd);
ToString() uses the current thread's Culture format to convert the date to a string, including the time. The format used is G, the general date and time format.
Just for this format, you don't need to specify CultureInfo.InvariantCulture because there isn't anything culture specific. A common gotcha with the yyyy/MM/dd format though is that some cultures use - as the date specifier, and / is the date placeholder. In such a case you would have to use:
string start = model.StartDate.ToString("yyyy-MM-dd,CultureInfo.InvariantCulture);
UPDATE
From the comments, it seems that model.StartDate and model.EndDate are not DateTime objects but strings with a specific format that include a time element.
What you are actually trying to do is parse the original string to a DateTime object, then format this object to the new format string:
var date=DateTime.ParseExact(model.StartDate,"M/d/YYYY HH:mm:ss tt",
CultureInfo.InvariantCulture);
model.StartDate=date.ToString("yyyy-MM-dd",CultureInfo.InvariantCulture);
assuming the string the value "4/1/2014 12:00:00 AM" for April 1, 2014
You appear to be misunderstanding how ParseExact works (or actually what it does). Parsing, in general, is the process of taking data of type X and converting it to type Y - in the context of DateTime this means converting a date string to a DateTime instance. This is completely different to what you are trying to do which is formatting a DateTime instance.
Given you already have the date you don't need to parse anything, all you need to do is format the date
model.StartDate.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture);
CultureInfo.InvariantCulture is important when working with fixed formats because you want to make sure you aren't culture aware i.e. the format you specify is exactly how you want it to display in all cultures.
Use the .Date property of a DateTime to get only the Date part. Your ToString() will also yield different results based on the current culture meaning that while your ToString() and then TryParse might work for you right now, it will break in other countries.
You can use ToString() overload to specify a specific format. Different formats can be found here
I have date string in format dd-MMM-yyyy and want to convert this to datetime, when I use below code
DateTime.ParseExact("20-Oct-2012", "yyyy-MM-dd HH:mm tt", null)
it causing an error
String was not recognized as a valid DateTime.
When I modify above code
DateTime.ParseExact("20-Oct-2012", "dd-MMM-yyyy", null)
then I got date time in format (mm/dd/yyyy) : 10/20/2012 12:00:00 AM
But I need it should be converted in yyyy/mm/dd format. Please help me in this regard.
You should try this
DateTime.ParseExact("20-Oct-2012", "dd-MMM-yyyy", null).ToString("yyyy/mm/dd")
For further reading on formats Check This
You need to distinguish between two separate concerns: that of parsing your original string into an abstract DateTime representation, and that of converting the latter back into another string representation.
In your code, you're only tackling the former, and relying on the implicit ToString() method call (which uses the system's current locale) to convert it back to string. If you want to control the output format, you need to specify it explicitly:
// Convert from string in "dd-MMM-yyyy" format to DateTime.
DateTime dt = DateTime.ParseExact("20-Oct-2012", "dd-MMM-yyyy", null);
// Convert from DateTime to string in "yyyy/MM/dd" format.
string str = dt.ToString("yyyy/MM/dd");
Also note that the mm format specifier represents minutes; months are represented by MM.
Edit: 'Converted date contain value "10/20/2012 12:00:00 AM".' Be careful what you mean by that. The constructed DateTime value contains an abstract representation of the parsed date and time that is independent of any format.
However, in order to display it, you need to convert it back into some string representation. When you view the variable in the debugger (as you're presumably doing), Visual Studio automatically calls the parameterless ToString() method on the DateTime, which renders the date and time under the current culture (which, in your case, assumes the US culture).
To alter this behaviour such that it renders the date and time under a custom format, you need to explicitly call the ToString(string) overload (or one of the other overloads), as I've shown in the example above.
You could try this instead :
Convert.ToDateTime("20-Oct-2012").ToString("yyyy/MM/dd")
Hope this will help !!
I am using the following function to determine whether input string is valid date or not.
public static bool IsDate(string date)
{
DateTime Temp;
if (DateTime.TryParse(date, out Temp))
return true;
else
return false;
}
Problem is when I give input "1997-09" then it returns true. I want it to check complete date like "1997-08-12"
And no there is no fix date format. Input could also be "19-Feb-2012"
And no there is no fix date format. Input could also be "19-Feb-2012"
There must be, otherwise it's nonesense. If you haven't defined how your system must behave you'd better stop coding and take a moment to define it.
You could use the TryParseExact method which allows you to specify one or more formats you would like to handle.
one easy condition you can add:
public static bool IsDate(string date)
{
DateTime Temp;
return(DateTime.TryParse(date, out Temp)&&date.Length>=10)
}
You should establish list of a correct date formats and then check with DateTime.TryParseExact, something like this:
string format = "yyyy-MM-dd";
DateTime dateTime;
if (DateTime.TryParseExact(dateString, format, CultureInfo.InvariantCulture,
DateTimeStyles.None, out dateTime))
Use DateTime.TryParse, you can specify the format then, more here. http://msdn.microsoft.com/en-us/library/9h21f14e.aspx
To resolve this you should define a datetime-format in your applicaiton.
On any webpage you go, if you see a compilation form, you probabbly will will see some date field too, and near it something like:
DD-MM-YYYY, or MM/DD/YY, or somethign else .
Define for your application format, make it esplicit for the user and check on correctness according to your format.
Just an hypothetic example:
say user inserted a date and you store it into the string like DD-MM-YYYY, one of possible choice could be simply say :
if(dateTimeUserString.Split('-').Length < 3)
//not valid string !
I repeat, this is just an example you should choose more appropriate way for your application.
DateTime.TryParse does have an overload that takes an IFormatProvider to allow specification of custom formats. You may need to define multiple IFormatPrividers to check the various strings you may expect as valid.
Also, rather than the if/else, you could also shorten your code a bit by
return DateTime.TryParse(date, out Temp);
You can return result of parsing directly:
public static bool IsDate(string value)
{
DateTime date;
return DateTime.TryParse(value, out date);
}
And it works with formats you have provided (at least when current culture "en-US").
Your code will run just fine and check the given date string if it can be a valid date using all of the current culture's date formats including this 19-Feb-2012 or 1997-09 of yours or even 19 february.
This makes you flexible in date input.
But if flexibility is not what your are looking for then try to parse for one or more specific formats using TryParseExact.
I need to perform some date operations in ASP.net using C#.
The date i would enter should be of format 'Jul-05' (mmm-yy Format and type-string)...
how can i check with this????
Or how can i validate this with whatever user is entering as a string???
After validating that, i need to compare tht with a value in Database(say a column name buy_period which has a value (say) 04/31/2007).
How can i write a Query for comparing both?? (as both dates would be of different formats)
Can u pls help me in this ???
DateTime myDateTime = DateTime.ParseExact( input, "MMM-yy" );
You can then happily pass it to a stored procedure (etc.) as a parameter to do your comparison on the server (or just use the DateTime returned as the result of an existing query)
Use the TryParseExact method to validate the string and parse it to a DateTime value:
DateTime month;
if (DateTime.TryParseExact("MMM-yy", CultureInfo.InvariantCulture, DateTimeStyles.None, out month)) {
// parsing was successful
}
The DateTime value will use the first day of month and the time 0:00 to fill up a complete value, so a string like "jul-05" will be parsed into a complete DateTime value like 2005-07-01 00:00:00.0000, so it will be the starting point of that month.
To compare this to a date in the database you also need the starting point of the next month, which you get with:
DateTime nextMonth = month.AddMonths(1);
Now you can just compare a date to the starting and ending point of the month in this manner:
where date >= #Month and date < #NextMonth
The .NET framework has some nice methods on the DateTime struct :: Parse, TryParse, ParseExact, TryParseExact.
This info is discussed on MSDN.
Becuase you're providing a custom date string, we should then use the ParseExact or TryParseExact. The later doesn't throw an exception if it fails to parse.
So.. lets try this...
using System.Globalization;
CultureInfo MyCultureInfo = new CultureInfo("en-US");
string myString = "Jul-05";
DateTime myDateTime = DateTime.ParseExact(myString, "MMM-yy", MyCultureInfo))
Console.WriteLine();
the value myDateTime can then be passed to a database as a DateTime property and checked against that.
EDIT: Damn, beaten by Rowland by a min, as i was typing it!
EDIT 2: Please note the "MMM-yy". As stated on the MSDN page, MMM is "Represents the abbreviated name of the month as defined in the current System.Globalization.DateTimeFormatInfo.AbbreviatedMonthNames property." mmm (lower case) is invalid.
1: read this
2: is the column is a datetime or varchar?
well your validation and comparison have to be two different operations. so you could do alot of things for validation.
Validation Options:
1.) Split your string on "-" and check to see if the mmm part is in your list of months, and then check to see if the number is valid.
2.) Regular Expression, this is advanced but can be reduced to one line. Look up RegEx if you are interested.
After you've validated the string, convert it to a DateTime object and compare it to the other value using DateTime.Compare().
Hope that helps.
You could use
DateTime date = DateTime.ParseExact(value, "MMM-yy", null); //checked at http://msdn.microsoft.com/en-us/library/8kb3ddd4.aspx
and then use that date in a sql command parameter.