I have the following method in order to verify whether a string is a valid datetime:
public bool isDate(string date)
{
bool check = false;
try
{
DateTime converted_date = Convert.ToDateTime(date);
check = true;
}
catch (Exception)
{
check = false;
}
return check;
}
Now, the exception "String was not recognized as valid datetime" is caught whenever I try to pass a string like this:
"12/31/2013 12:00:00 AM"
I cannot understand why this is happening. Can someone help me solve this please?
Instead of the try/catch block, try the built in TryParse method in the DateTime class. It takes your string as a parameter and if it converts successfully it will place the value in the "result" variable. It returns a boolean value representing whether it worked or not.
public bool isDate(string date)
{
var result = new DateTime();
return DateTime.TryParse(date, out result);
}
Most likely your current culture settings are different from the format date is provided in. You can try specifying the culture explicitly:
CultureInfo culture = new CultureInfo("en-US"); // or whatever culture you want
Convert.ToDateTime(date, culture);
You can also use DateTime.TryParseExact and pass a format string (eg. MM/dd/yy H:mm:ss zzz, see more here) to check if the date has a specific format.
Related
I want to check if a given string is a valid .net date format.
so i have the following function that checks if the date format is correct
public void IsValidDateFormat(string dateFormat)
{
var flag = true;
try
{
DateTime.ParseExact(DateTime.Now.ToString(),
dateFormat,
System.Globalization.CultureInfo.InvariantCulture);
}
catch (Exception ex)
{
flag = false;
}
return flag;
}
However, The method is not working as expected. For a valid date format also it returns false.
dateFormat = ,, => returns false =>Passed
dateFormat = someinvalidformat => returns false =>Passed
dateFormat = MM/dd/yyyy => returns false => Not Passed
So MM/dd/yyyy is valid dateformat. But method returns false.
Is there a better way to check if given date format is valid .Net date format?
Update 1
I understand why method fails for MM/dd/yyyy or for other valid date formats. I am not asking why it fails. MM/dd/yyyy is just common valid date time format i am using here for example.
I am looking for a way to check if the given date format is valid .Net date format. So it could be any .Net date format.
Since the format returned by DateTime.ToString does not match your format (it includes the time part), ParseExact fails.
Validate the format by using public string ToString(string format, System.IFormatProvider provider) instead
public bool IsValidDateFormat(string dateFormat)
{
try {
string s = DateTime.Now.ToString(dateFormat, CultureInfo.InvariantCulture);
DateTime.Parse(s, CultureInfo.InvariantCulture);
return true;
} catch {
return false;
}
}
Note that date/time formats that may seem not to be valid, can in fact be valid, as some non-format characters are just outputted as is. E.g.
DateTime.Now.ToString("abcdefg", CultureInfo.InvariantCulture)
results in "abc27e6A.D.". So it is in fact a valid date/time format, even if it does not make a lot of sense. You can enhance the quality of the test by trying to parse the resulting date string. This will eliminate a lot of nonsensical formats.
This test ...
Console.WriteLine(IsValidDateFormat(",,"));
Console.WriteLine(IsValidDateFormat("a"));
Console.WriteLine(IsValidDateFormat("MM/dd/yyyy hh:mm:ss"));
Console.WriteLine(IsValidDateFormat("MM/dd/yyyy"));
Console.WriteLine(IsValidDateFormat("abcdefg"));
Console.ReadKey();
... prints
False
False
True
True
False
why not TryParse() or exact version? https://learn.microsoft.com/es-es/dotnet/api/system.datetime.tryparse?view=netframework-4.8
returns true if system can parse.
It does "the same" your method does.
I want to display a message only when the datetime is before or on todays date. Here is what I have:
var todaysdate = DateTime.Today;
if (acct.maturityDate <= todaysdate )
{
maturityText.Visible = true;
}
I get a message saying that (acct.maturityDate <= todaysdate ).
Cannot apply operator '<=' to operands of type 'string' and 'system.datetime', candidates are bool <=(system.datetime,system.datetime) (in struct datetime).
Any help is appreciated.
As the error says, maturityData is a string and not a DateTime you need to convert it:
var todaysdate = DateTime.Today;
if (DateTime.Parse(acct.maturityDate) <= todaysdate ) {
maturityText.Visible = true;
}
I'm making a direct parse there, you might want to consider TryParse or ParseExact depending on your needs.
This means that the property acct.maturityDate is of the type string and not the expected type System.DateTime. Convert/parse the property to a DateTime and your problem should be solved, or make sure the property is already a DateTime.
As mentioned in my comment, the type of maturityDate is a string. using DateTime.Parse() would allow you to resolve your issues and so will DateTime.TryParseExact()
Converting to the correct type will allow you to use the correct operators.
Firstly you have to change maturityDate to DateTime type, and then you should use DateTime.Compare method you can refer to this link
If maturityDate must be left as-is, you can either use the DateTime.Parse, DateTime.TryParse, or DateTime.TryParseExact methods.
Parse will throw an exception if maturity date cannot be parsed.
TryParse and TryParseExact will not throw exceptions, but will allow you to make a decision based on whether the date is able to be parsed.
TryParseExact allows you to parse your date even if it doesn't match a standard DateTime format. You simply specify the format string, as well as culture and style information, in the method parameters.
Parse Example:
var todaysdate = DateTime.Today;
if (DateTime.Parse(acct.maturityDate) <= todaysdate ) {
maturityText.Visible = true;
}
TryParse Example:
var todaysdate = DateTime.Today;
DateTime dt;
if (DateTime.TryParse(acct.maturityDate, out dt)
{
if (dt <= todaysdate)
{
maturityText.Visible = true;
}
}
TryParseExact Example:
var todaysdate = DateTime.Today;
DateTime dt;
// use whatever format string matches appropriately
if (DateTime.TryParseExact(acct.maturityDate, "YYYY-MM-dd HH:mm:ss"
, CultureInfo.InvariantCulture
, DateTimeStyles.None, out dt)
{
if (dt <= todaysdate)
{
maturityText.Visible = true;
}
}
I have a function that checks for null values then converts dates if they are not null
the below function just had "08/09/13" sent to it (English format) and i got "String was not recognized as a valid DateTime."
anyone help me as to why? do i need to tell the something somewhere is uses English format?
Thanks
public static DateTime DateTimeCheck(object objDateTime)
{
if (objDateTime == null || objDateTime == "")
return default(DateTime);
return Convert.ToDateTime(objDateTime);
}
I don't understand why you passed an object as a parameter instead of string first of all.
Try this instead;
public static DateTime DateTimeCheck(object objDateTime)
{
...
return DateTime.ParseExact(objDateTime.ToString(),"dd/MM/yy",CultureInfo.InvariantCulture);
}
Of course, this throws exception if your object is not formatted same as with "dd/MM/yy".
Take a look at;
Custom Date and Time Format Strings
You can use the overloaded method that accepts the culture information:
Convert.ToDateTime(o, new CultureInfo("en-Gb"));
To get or set the current culture you can use:
System.Threading.Thread.CurrentThread.CurrentCulture
You might be in a different culture with a different default date format. However you can use ParseExact to parse in the expected format. For example:
CultureInfo provider = CultureInfo.InvariantCulture;
DateTime result = DateTime.ParseExact("25/12/82","dd/MM/yy",provider);
I know this not what you are looking for but that's how to be sure that some object has date time value in it something like that :
public static DateTime DateTimeCheck(object objDateTime)
{
DateTime dateTime ;
if (objDateTime != null)
{
if (DateTime.TryParse(objDateTime.ToString(), out dateTime))
{
return Convert.ToDateTime(objDateTime);
}
}
return default(DateTime);
}
Try this:
DateTime.ParseExact((string)objDateTime,"dd/MM/yyyy",CultureInfo.InvariantCulture);
I'm trying to convert a string to datetime to validate if user input is actually a date.
The error I'm getting is:
Cannot implicitly convert type bool to System.DateTime.
I've been looking online for a while and can't find anything specific enough to help me understand.
Code:
public bool is21YearsOfAge(string argument)
{
DateTime _parsedDateArgument;
DateTime convertStringToDate = System.DateTime.TryParse(argument, out >_parsedDateArgument);
if (convertStringToDate > DateTime.Now)
{
//do something
}
}
Thanks in advance.
The TryParse method returns a bool that informs you whether the parse was successful, rather than throwing an exception like the Parse method does. Try doing this:
DateTime convertStringToDate;
bool isDate = DateTime.TryParse(argument, out convertStringToDate);
If argument is a date, convertStringToDate will contain that date as a DateTime.
DateTime.TryParse returns bool to indicate if parsing was successeful. So you should do
System.DateTime.TryParse(argument, out _parsedDateArgument);
DateTime convertStringToDate =_parsedDateArgument
Look at the documentation for DateTime.TryParse - it returns a bool, but has an out parameter for the parsed result:
DateTime dateTime;
bool success = DateTime.TryParse(text, out dateTime);
If success is false, that means the text couldn't be parsed. (So typically at this point you'd display an error to the user.)
You've already got the out parameter - why did you expect to end up with two different DateTime values (one as the return value and one from the out parameter)?
When you get an error like this, always read the documentation as the first step towards diagnosing the problem.
It should be
DateTime convertStringToDate;
if(System.DateTime.TryParse(argument, out convertStringToDate))
{
//Now you will have converted date in convertStringToDate
if (convertStringToDate > DateTime.Now)
{
//do something
}
}
else
{
//argument not have a valid date
}
System.DateTime.TryParse will retrun true if, argument will have a valid date string to convert. and the converted date will be store in its out parameter.
DateTime.TryParse do not return a DateTime value. It returns a bool indicating if it could parse it.
Instead use
DateTime convertStringToDate;
if(DateTime.TryParse(argument, out convertStringToDate)){
//ok value is good
}else{
//Not ok value is not good
}
use this instead,
DateTime _parsedDateArgument;
bool success = System.DateTime.TryParse(argument, out _parsedDateArgument);
Always remember that Tryparse always return boolean.
TryParse returns a bool, use just Parse instead, or assign the out variable to the new you have:
System.DateTime.TryParse(argument, out _parsedDateArgument);
DateTime convertStringToDate = _parsedDateArgument;
or like this:
DateTime convertStringToDate = DateTime.Parse(argument);
add the following namespace
using System.Globalization;
Create object of CultureInfo class
CultureInfo MyCI = new CultureInfo("en-US");
DateTime convertStringToDate = System.DateTime.TryParse(argument.ToString("MM/dd/yy", MyCI), out _parsedDateArgument);
I'm trying to convert dates for example 30/12/2000 to 2000-12-30
using this code:
System.Globalization.CultureInfo enUS = new System.Globalization.CultureInfo("en-US");
DateTime.ParseExact(row.Cells[6].ToString(), "yyyy-MM-dd", enUS);
But I'm getting this error:
String was not recognized as a valid DateTime.
Can someone help me please, Thank you in advance.
You could use DateTime.TryParse() function and check if result is true or false.
So you could try to parse date with a specified format and, if its not right, try another one and so on...
The reason why you are getting this is exactly as the exception says, the string is in an incorrect format, the reason is most likely that the machine doing the comparison has a different date time setting to yyyy-MM-dd.
If you are retrieving this from a database and the return value is of date time (or if you know that row.Cells[6] is a DateTime Field, the following should work:
System.Globalization.CultureInfo enUS = new System.Globalization.CultureInfo("en-US");
if (row.Cells[6] != null)
DateTime.ParseExact(((DateTime)row.Cells[6]).ToString("yyyy-MM-dd"), "yyyy-MM-dd", enUS);
The question is however why would you want to change the format, to display it on a form if so then you can just display it as follows:
if (row.Cells[6] != null)
TextBox1.Text = ((DateTime)row.Cells[6]).ToString("yyyy-MM-dd");
EDIT
Given that row.Cells[6] is a string, you will always have to know what the format of the string is, and if you do then it would be as simple as:
With time:
DateTime ParsedDate = DateTime.ParseExact(row.Cells[6].ToString(), "dd-MM-yyyy h:mm", enUS);
Removing time and then parsing:
DateTime ParsedDate = DateTime.ParseExact(row.Cells[6].ToString().Substring(0,10), "dd/MM/yyyy", enUS);
and then to output it in the format you want would be as simple as:
TextBox1.Text = ParsedDate.ToString("yyyy-MM-dd");
You are specifying a en-US CultureInfo object, but 30/12/2000 is not a correct US date format
Try this may resolve your issue
String oldScheduledDate = "16-05-2011";
DateFormat oldFormatter = new SimpleDateFormat("dd/MM/yyyy");
DateFormat formatter = new SimpleDateFormat("yyyy/MM/dd");
try
{
Date oldDate = (Date)oldFormatter .parse(oldScheduledDate);
}
Catch(Exception ex ) { /// process exception}
System.Globalization.CultureInfo enUS = new System.Globalization.CultureInfo("en-US");
try {
DateTime.ParseExact(row.Cells[6].ToString(), "yyyy-MM-dd", enUS);
}
catch (FormatException) {
...your code instead of error...
}
I believe that the problem is your second parameter. If you are passing 30/12/200 as your input, it will fail because the second parameter is expecting it separated with dashes.
use
System.Globalization.CultureInfo.InvariantCulture
DateTime.ParseExact(((DateTime)row.Cells[6]).ToString("yyyy-MM-dd"), "yyyy-MM-dd", System.Globalization.CultureInfo.InvariantCulture)
;
you forgot the hours / minutes:
from the DB it comes like that (converted to string) "12/05/2011 0:00"
DateTime.ParseExact(theCellValue, "MM/dd/yyyy HH:mm", enUS).ToString("yyyy-MM-dd")
creates the string you want, but its totally stupid. you should just make sure that the datetime gets in the first place formatted as you want. (then you never have to parse it)
If your source string is in dd/MM/yyyy, then you shouldn't be using US culture (MM/dd/yyyy) to parse the string.
System.Globalization.CultureInfo enGB = new System.Globalization.CultureInfo("en-GB");
DateTime temp = DateTime.ParseExact(row.Cells[6].Text, "dd/MM/yyyy", enGB);
row.Cells[6] = temp.ToString("yyyy-MM-dd");
Put this in the RowDataBound event of your grid.
I fixed it by using
Convert.ToDateTime(row.Cells[6].Text)
See how simple it is.