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.
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 have the following code -
DateTime timeStamp;
timeStamp = System.Convert.ToDateTime(y.InnerText);
Where y.InnerText is 11/03/2013 11:35:24.
However this is breaking my import statement as it the database is looking for the format -
2013-03-11 11:35:24
How can I set the format of the DateTime object?
How can I set the format of the DateTime object?
You can't. DateTime values don't have formats, any more than int or double values do. When you want to convert them to/from strings, that's where you specify any formatting information.
Instead, you should use parameterized SQL and avoid converting the DateTime value back into a string in the first place. This is a general best practice - don't include values in your SQL string; parameterized SQL has multiple benefits:
It avoids SQL injection attacks
It avoids conversion issues like this one
It keeps your code (SQL) separate from your data (parameter values)
I would also suggest that instead of using Convert.ToDateTime, you specify your expected format when parsing. For example:
timeStamp = DateTime.ParseExact(y.InnerText,
"dd/MM/yyyy HH:mm:ss",
CultureInfo.InvariantCulture);
Basically, the two rules I try to apply are:
Avoid performing any conversions where you don't have to. If you make sure that every system uses the right data types as far as possible, you often don't need to make any conversions at all.
Where you do need to convert to/from string representations, be very explicit about the representation you want to consume/produce. For machine-readable values, that should usually use the invariant culture and possibly a custom date/time format. For human-readable values, that should usually use the user's culture and a standard date/time format.
I use this step
Convert to DateTime.
Use ToString(); function
Example :
DateTime myDateTime = DateTime.Now;
string myDateTimeString = myDateTime.ToString("yyyy-MM-dd hh:mm:ss");
if you are passing datetime to sql database try with yourdatetime.ToString("yyyy/MM/dd") format this will work for you.
and one more thing you can add a datetime format for your Applicaton culture. so this will treat you datetime format at you desire.
using System;
using System.Globalization;
using System.Threading;
namespace test {
public static class Program {
public static void Main() {
CultureInfo culture = (CultureInfo)CultureInfo.CurrentCulture.Clone();
culture.DateTimeFormat.ShortDatePattern = "yyyy/MM/dd HH:mm:ss";
culture.DateTimeFormat.LongTimePattern = "";
Thread.CurrentThread.CurrentCulture = culture;
Console.WriteLine(DateTime.Now);
}
}
}
Basically Date does not have a format. If the database parameter/field is Datetime type you should be fine passing as a Date type. It is not a good idea to pass date as a string.
However, if that something you have to deal with, then you better pass the Date in a none culture specific date format (ISO8601 or ISO) in a parameterised query. Otherwise you could have problems with database servers in different culture settings.
For example, for sql server, it is safe (in conversion) to pass date time in ISO8601 as;
'yyyy-mm-ddThh:mi:ss.mmm' //(no spaces)
you can use ToString convertion to 2013-03-11 11:35:24
DateTime timeStamp;
timeStamp = System.Convert.ToDateTime(y.InnerText).ToString("yyyy-MM-dd HH:mm:ss");
And what if you just override your ToString() method of your DateTime object?
Wouldn't you be able then to choose the format you want and every time it is used, it will be formatted in the way you want it without being bothered by it.
This is just a thought so I don't know if there are better solutions or not.
You can then use the properties year, month, day, to build it like you want.
Something like:
public override ToString(){
return this.Year + "-" + this.Month + "-" + this.Day;
}
Greetings
I'm trying to format a list of datetime. One date is in the format same as what i provided but the factors are not in place. That line of code is given below. Can someone tell me how to skip the error for the below line?
Convert.ToDateTime("22-01-2013 00:00:00").ToString("yyyy-MM-dd");
I would avoid using Convert.ToDateTime to start with. I would suggest using DateTime.TryParse or (preferrably) DateTime.TryParseExact. Both of these will return a value indicating whether the conversion succeeded, so you don't need to start catching exceptions in order to skip bad data. For example:
DateTime parsed;
if (DateTime.TryParse(text, out parsed))
{
string reformatted = parsed.ToString("yyyy-MM-dd");
// Use reformatted
}
else
{
// Log error, perhaps?
}
If you have multiple possible formats, you should consider using the overload of TryParseExact which allows you to specify multiple formats in a single call.
As well as the format, you should consider the culture you want to use. In the above code (and your code) it will use the executing thread's culture. Is that always what you want? The culture can affect all kinds of things - usually if you're specifying a custom format, you want to use the invariant culture. Otherwise you could end up using a non-Gregorian calendar unexpectedly, for example...
EDIT: If your input is always in the format dd-MM-yyyy, then you should probably use:
DateTime parsed;
if (DateTime.TryParseExact(text, "dd-MM-yyyy", CultureInfo.InvariantCulture,
DateTimeStyles.Default, out parsed))
{
string reformatted = parsed.ToString(CultureInfo.InvariantCulture,
"yyyy-MM-dd");
// Use reformatted
}
else
{
// Log error, perhaps?
}
Instead of Convert.ToDateTime use DateTime.Parse or DateTime.ParseExact
ParseExact gives you more control over the format, so for example:
DateTime.ParseExact("22-01-2013 00:00:00","dd-MM-yyyy HH:mm:ss",CultureInfo.InvariantCulture).ToString("yyyy-MM-dd");
There is also a TryParseExact variant, which allows you to gracefully handle parse errors.
Try with:
DateTime.ParseExact("22-01-2013 00:00:00","dd-MM-yyyy HH:mm:ss",CultureInfo.InvariantCulture).ToString("yyyy-MM-dd");
This way you can specify the exact format for your date-string.
Try to use DateTime.ParseExact() method instead of.
Converts the specified string representation of a date and time to its
DateTime equivalent.
public static void Main(string[] args)
{
Console.WriteLine(DateTime.ParseExact("22-01-2013 00:00:00", "dd-MM-yyyy HH:mm:ss", CultureInfo.CurrentCulture).ToString("yyyy-MM-dd"));
}
Here is a DEMO.
Also check out Coding Best Practices Using DateTime in the .NET Framework which I think every .NET developer should read.
I have a string I need to convert back to a date. I can call .ToString("yyyyMMdd") and get the string i want. My question is how can I convert that back into a date? I'm trying something like the following with no luck.
DateTime d;
var formatInfo = new DateTimeFormatInfo {ShortDatePattern = "yyyyMMdd"};
if (DateTime.TryParse(details.DetectionTime.Date, formatInfo, DateTimeStyles.None, out d))
{
lit.Text = d.ToShortTimeString(); //would like 07/30/2010 as the text
}
I've never used DateTimeFormatInfo before if that isn't obvious. Can someone point me in the right direction. I know I could probably use substring and create a new DateTime(y, m, d) etc... I'm just wondering since c# interpreted .ToString() correctly, if it can't derive a date from the very same string it output.
The reverse of DateTime.ToString("yyyyMMdd") is DateTime.TryParseExact, passing "yyyyMMdd" as a format string.
IFormatProvider is a bit of a red herring. You'll normally pass either :
Thread.CurrentThread.Culture, if you're parsing a date typed by the user, when you should obey the user's date preferences
Or CultureInfo.InvariantCulture, if you're parsing a date provided by a program, when your behaviour shouldn't depend on the preferences the user has set up
Use d.ToString("MM/dd/yyyy")
For more options check out http://msdn.microsoft.com/en-us/library/zdtaw1bw.aspx
Edit: Read it wrong
Use DateTime.Parse() to parse the string to a datetime.
http://msdn.microsoft.com/en-us/library/1k1skd40.aspx
You can also use DateTime.TryParse to see if the string is able to convert to a date first.
http://msdn.microsoft.com/en-us/library/system.datetime.tryparse.aspx
Alternatively you can also use Convert.ToDateTime()
If you want the DateTime variable back after sending it to a string, save yourself the trouble and just cache or pass the actual DateTime variable around scopes to wherever you need it later and don't bother converting the text back into a DateTime class..
Sorry I just realized this doesn't answer your request, so what you're looking for is:
DateTime.ParseExact(someDateTime, "the format string you used to .tostring generating the string", null);
Convert.ToDateTime("07/30/2010");
I'm assuming you mean to convert a string to a DateTime format. If so use this:
DateTime yourStringConverted = Convert.ToDateTime( yourString );
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.