What is the best way to compare two DateTime in a specific format and trigger code if DateTime has passed.
My DateTime is formatted as 4/26/2017 10:00:00 AM
DateTime currentDateTime = DateTime.Now;
DateTime eventDateTime = DateTime.Parse("4/26/2017 10:00:00 AM");
int result = DateTime.Compare(currentDateTime, eventDateTime);
if (result < 0)
Response.Write( "is earlier than Do Nothing");
else if (result == 0)
Response.Write("is the same time as: Do Nothing");
else
Response.Write("Time is greater, Trigger Action ");
Is the above code fine for comparison or we can improve it.
For my opinion, the method you suggested is the most efficiant and accepted way to compare 2 DateTime variables in C#, considering you need to take action if the 2 dates are also equal.
Side note:
If you only needed to compare the 2 DateTime without the equal condition, you could just write:
if (currentDateTime < eventDateTime)
Response.Write("is earlier than Do Nothing");
else
Response.Write("Time is greater, Trigger Action");
which is a bit cleaner and more efficiant.
To compare Dates, your method is efficient one because according to MSDN
The CompareTo method compares the Ticks property of the current instance and value but ignores their Kind property. Before comparing DateTime objects, make sure that the objects represent times in the same time zone.
So as it does compare Ticks of two instances of DateTime, so it is the efficient method for comparison.
As a side note, if you want to find interval between DateTime Instances then you can use DateTime.Subtraction it will give TimeSpan of both DateTime instances. So you can find total difference in their minutes, hours, days, seconds, milliseconds by using TimeSpan properties.
DateTime date1 = new DateTime(2010, 1, 1, 8, 0, 15);
DateTime dateNow = DateTime.Now;
TimeSpan interval = dateNow.Subtract(date1);
double totalHours= interval.TotalHours;
double totalMinutes = interval.TotalMinutes;
double totalSeconds= interval.TotalSeconds;
double totalMilliseconds= interval.TotalMilliseconds;
You can use nested if else statement as below:
if (currentDateTime < eventDateTime)
Response.Write("is earlier than Do Nothing");
else if(currentDateTime > eventDateTime)
Response.Write("time is greater, Trigger Action");
else
Response.Write("is the same time as: Do Nothing");
Related
I'm new to C# and I'm trying to write a simple console application. I have two datetimes but I can't get the message Same, It keeps printing Different.
I also print the two datetimes in the console to know if they are different, but even when the system time is the same it doesn't satisfy the condition.
static void Main(string[] args)
{
while (true)
{
Thread.Sleep(1000);
DateTime dt1 = DateTime.Now;
DateTime dt2 = DateTime.Parse("06:30:00 AM");
if (TimeSpan.Compare(dt1.TimeOfDay, dt2.TimeOfDay) == 0)
{
Console.WriteLine("Same");
}
else
{
Console.WriteLine("Different");
}
Console.WriteLine(dt1);
Console.WriteLine(dt2);
}
}
DateTime has a resolution down to ticks, even though by default they're only printed to seconds in most cultures.
If you print dt1.ToString("o") and the same for dt2, you'll see that even if they're equal to the second, they may well vary in sub-second amounts. That explains why your current code can print "different" but then still print the same value for the next two lines.
A DateTime carries alot more precision than seconds, it is based on ticks, where each tick is 100 nanoseconds. So even if the DateTime.Now matches in hours minutes and seconds, it will be way off in ticks.
You'd be better off using > or < when you attempt to compare. Or do (a - b) < some timespan! Something like:
DateTime dt1 = DateTime.Now;
DateTime dt2 = DateTime.Parse("06:30:00 AM");
bool matches = ( dt2 - dt1 ).Duration() < TimeSpan.FromMilliseconds( 100 ); // matches if dt1 and dt2 are within 0.1s
The .Duration() call is needed to get an absolute time span that can't be negative. Note that you should never use this method for something like an alarm, your system could briefly freeze (due to a multitude of possibilites) and you'd miss it.
Your current comparison would compare Ticks for both DateTime object. If you want to compare Hour, Minute and seconds then have a check like:
if (dt1.TimeOfDay.Hours == dt2.TimeOfDay.Hours &&
dt1.TimeOfDay.Minutes == dt2.TimeOfDay.Minutes &&
dt1.TimeOfDay.Seconds == dt2.TimeOfDay.Seconds)
I want to compare between two dates.
From both the dates, I am fetching only date component using ToShortDateString(), as shown below. Now the problem is when I'm comparing the two dates. Its throwing error --
"Operator >= can't be applied to operands of type string and string."
DateTime srtdate = Convert.ToDateTime(allitem["StartDate"].Text.ToString());
DateTime srtdate = Convert.ToDateTime(allitem["StartDate"].Text.ToString());
(DateTime.Now.ToShortDateString() >= srtdate.ToShortDateString())
I need to compare date component only, NOT date and time together.
Please suggest what is the alternative way. Thanks
To JON:-
(I went tyhrough all what you explained and understood hopefully what the point actually you trying to make. Just to clarify more and make a last check I ll show an example.)
I have an web interface, where I give a start date and end date for a XYZ name (Note I can enter only date here, not time).
Start Date - 22-Feb-2012 AND End Date - 22-Feb-2012
Now in back end (code), if Start date and End date is same as Current date OR current date is in between start and end date, I want a ACTIVE flag set or else not. I give the condition as this:-
if ((DateTime.Today >= strdate.Date) && (DateTime.Today <= enddate.Date))
lblCondition.Text = "CHECKED";
Now when I debug the code,
Both DateTime.Today and strdate.Date gives the value as 2/22/2012 12:00:00 AM.
So, Jon my question is:- Would 'today' and 'date' work as per mentioned requirement, where only date component used. I hope it would.
Thanks a lot for all your explanantion before.
Why are you converting to a string representation at all? If you only want to compare the date parts to two DateTime values, just use the Date property on each of them:
if (x.Date >= y.Date)
And the Today property is equivalent to DateTime.Now.Date.
Both Date and Today strip off the time part, leaving a time of midnight. It's not ideal that you've still got a type which is capable of representing times, but that's just the way the DateTime API works :(
Note that you should usually avoid using DateTime.Now or DateTime.Today in web applications unless you're really comfortable with it using the system default time zone as the day boundary. The user's idea of "today" may not be the same as the server's.
You should avoid using string conversions unless your goal is really to get a text representation.
Of course another alternative would be to use the date/time library I'm building, Noda Time, where you could use a LocalDate type - obviously that makes it clearer that you're only interested in the date and not the time.
EDIT: As the OP seems unconvinced that Date really does ignore the time component, here's an example:
using System;
public class Test
{
static void Main()
{
// Two DateTime values with different times but
// on the same date
DateTime early = new DateTime(2012, 2, 22, 6, 0, 0);
DateTime late = new DateTime(2012, 2, 22, 18, 0, 0);
Console.WriteLine(early == late); // False
Console.WriteLine(early.Date == late.Date); // True
}
}
DateTime.Today >= strdate.Date
some thoughts
Think at the the following example: you need to compare the following numbers 1.5 and 2.5. These are represented in .Net as decimal, double or float, but let's use decimal. The greater one is 2.5
Let's say you need to compare the integral part of these numbers (1. and 2.). You will still use the decimal type to do the comparison.
Math.Truncate(x) ? Math.Truncate(y) // x = 1.5, y = 2.5
Same as for the DateTime. DateTime.Date will return the "integral" part of your date as Math.Truncate returns the integral part of a "real" number, but both will base on their original type.
hope this helps you.
using System;
public class Example
{
public static void Main()
{
DateTime date1 = new DateTime(2009, 8, 1, 0, 0, 0);
DateTime date2 = new DateTime(2009, 8, 1, 12, 0, 0);
int result = DateTime.Compare(date1, date2);
string relationship;
if (result < 0)
relationship = "is earlier than";
else if (result == 0)
relationship = "is the same time as";
else
relationship = "is later than";
Console.WriteLine("{0} {1} {2}", date1, relationship, date2);
}
}
// The example displays the following output:
// 8/1/2009 12:00:00 AM is earlier than 8/1/2009 12:00:00 PM
I'm trying to get the number of days (calculated byu datediff) in sql and the number of days in c# (calculated by DateTime.now.Substract) to be the same, but they return different results....
//returns 0
int reso = DateTime.Now.Subtract(expirationDate).Days;
vs
//returns 1
dateDiff(dd,getDate(),ExpirationDate)
In both cases, ExpirationDate is '10/1/2011 00:00:00', and the code and the DB are sitting on the same server. I want the return int to be the same. I suspect I'm missing something stupid... ideas??
dateDiff(dd,getDate(),ExpirationDate) Is doing a days comparison. DateTime.Now.Subtract(expirationDate).Days is doing a date and time
For example
SELECT dateDiff(dd,'10/1/2011 23:59:00' , '10/2/2011') returns one day even when only one minute apart.
If you want the same in C# you need to remove the time component
e.g.
DateTime dt1 = new DateTime(2011,10,1, 23,59,0);
DateTime dt2 = new DateTime(2011,10,2, 0,0,0);
Console.WriteLine((int) dt2.Subtract(dt1.Subtract(dt1.TimeOfDay)));
So in your case it would be something like
DateTime CurrentDate = DateTime.Now;
int reso = CurrentDate.Subtract(CurrentDate.TimeOfDay).Subtract(DateTime.expirationDate).Days;
I haven't tested it but I would not do
DateTime.Now.Subtract(DateTime.Now.Subtract.TimeOfDay)
Because the second call to Now wouldn't be guaranteeing to be the same as first call to Now
In any case Stealth Rabbi's answer seems more elegant anyway since you're looking for a TimeSpan not a DateTime
10/1/2011 is less than 1 day away from DateTime.Now. Since you're getting back a TimeSpan and then applying Days to it, you're getting back a TimeSpan that is < 1 day. So it'll return 0 Days.
Instead, just use the Date component of those DateTimes and it'll correctly report the number of days apart - like this:
DateTime now = DateTime.Now;
DateTime tomorrow = new DateTime(2011, 10, 1);
var val = (tomorrow.Date - now.Date).Days;
This will yield you 1 day.
I'm assuming you want the number of Total days, not the number of days from the largest previous unit. You'd want to use the TotalDays property. Also, you may find it easier to use the minus operator to do a subtraction
DateTime d1 = DateTime.Now;
DateTime d2 = new DateTime(2009, 1, 2);
TimeSpan difference = d1 - d2;
Console.WriteLine(difference.TotalDays); // Outputs (today):1001.46817997424
I am creating a function that will set the date of an event, based on the current time.
I have an enumeration of events:
public enum EventTimings
{
Every12Hours, // 12pm and midnight
Weekly // sunday at midnight
}
public static DateTime CalculateEventTime(EventTimings eventTime)
{
DateTime time;
switch(eventTime)
{
case EventTimings.Every12Hours:
break;
}
return time;
}
So (Every12Hour event type) if the current time is 10am, then the eventdate will be the same day but at 12pm.
How should I write this?
I also have to make sure this works for December 31st and any other strange outlier date/time.
Is datetime the best for this scenerio?
If you want to be able to test anything, I would make the DateTime you are trying to "round" explicit, something like
public static DateTime RoundedDate(DateTime eventTime, EventTimings strategy)
{
switch (strategy)
case EventTimings.Weekly :
return WeeklyRounding(eventTime);
... etc ...
That way you can now write a specialized method for the 12-hour interval, the week interval, and test it for any input date possible, without depending on your computer clock.
You could also try something like this, although it breaks down if you want to do something monthly (because months each have a different number of days.) Also, while this simplified method will ensure a returned date at 12 and midnight, the weekly offset would be every 7 days from the starting day... not necessarily on Sundays. You could easily accomodate that behavior with a switch statement, though. The overloaded method also allows you some flexibility to provide a custom offset.
Also, to answer your question, yes I would use System.DateTime and System.TimeSpan. They handle determining whether a year or month has "rolled over" for you.
public enum EventTimings : int
{
Default = 12, // Default every 12 hours.
NoonAndMidnight = 12, // Every 12 hours.
Weekly = 168, // 168 hours in a week.
ThirtyDays = 720 // 720 hours in 30 days.
}
public DateTime CalculateDateTime(DateTime starting, EventTimings timing)
{
return CalculateDateTime(starting, TimeSpan.FromHours((int)timing));
}
public DateTime CalculateDateTime(DateTime starting, TimeSpan span)
{
DateTime baseTime = new DateTime(starting.Year, starting.Month, starting.Day, starting.Hour >= 12 ? 12 : 0, 0, 0);
return baseTime.Add(span);
}
I agree to keep it generic by making the reference date an input parameter instead of current datetime. However as you have asked about the logic for your eventTime values as well, this is how I would go about.
How should I write this?
For every12hours, check the hour property of the input date and check if it is less than 12. If so, then create a new TimeSpan for 12pm and add it to the datepart of the input date.
If not, add 1 day to the input date, create a TimeSpan for 12am and add it to the datepart of inputdate.
For weekly (Monday 12am), check the dayoftheweek of the inputdate and just add number of days to make it equal to the incoming Monday (Which is as simple as (8 - dayoftheweek)) and add a 12am TimeSpan to the date of the incoming Monday's date.
public enum EventTimings
{
Every12Hours, // 12pm and midnight
Weekly // sunday at midnight
}
public static DateTime CalculateEventTime(EventTimings eventTime, DateTime inputDate)
{
DateTime time = DateTime.Now;
switch (eventTime)
{
case EventTimings.Every12Hours:
time = inputDate.Hour > 12 ? inputDate.AddDays(1).Date + new TimeSpan(0, 0, 0) : inputDate.Date + new TimeSpan(12, 0, 0);
return time;
case EventTimings.Weekly:
int dayoftheweek = (int) inputDate.DayOfWeek;
time = inputDate.AddDays(8 - dayoftheweek).Date + new TimeSpan(0, 0, 0);
return time;
// other cases
}
}
Is datetime the best for this scenerio?
Yes. Your datetime calculations using DateTime and TimeSpan should take care of leap years, daylight savings or endofyear scenarios. Additionally you could try adding SpecifyKind to denote it is local time.
The algorithm I'd follow goes like this...
Put noon on the day of eventTime into a variable
Check if that variable is before eventTime
If it's not, add 12 hours to it
Return the variable
switch (strategy)
{
case EventTimings.Every12Hours:
//get noon for the event date
DateTime x = eventTime.Date.AddHours(12);
//check to see if x is after the eventTime
if (x < eventTime)
{
//if so, advance x by 12 hours to get midnight on the next day
x = x.AddHours(12);
}
return x;
break;
//other cases...
}
Goal - find out which DateTime is more recent.
Can I figure this out with this code:
DateTime dt1 = new DateTime(...); //let's say it was created on 1/1/2000
DateTime dt2 = new DateTime(...); //let's say it was create on 1/1/2011
if (dt2.ToBinary() > dt1.ToBinary()) {
print dt2 is newer than dt1 }
Can I simply convert the DateTime objects to binary, then presume that the larger one is more recent?
Thanks,
Kevin
if (dt2 > dt1) {
print dt2 is newer than dt1 }
should be enough as DateTime overloads the comparison operators.
You can usually do better than that:
if (dt2 > dt1)
The tricky bit is taking time zones into consideration... you can potentially use
if (dt2.ToUniversalTime() > dt1.ToUniversalTime())
but only if you know that any "local" times really are local in the system's time zone.
Dates and times in .NET are a bit of a mess :(
No, you can't. ToBinary() returns an internal format that also stores time zone info.
Instead, you can compare the DateTimes directly:
if (dt2 > dt1)
DateTime overloads the comparison operators.
You could compare the Ticks property, but you shouldn't bother.
You can use Datetime.Compare
int iDiff = DateTime.Compare(new DateTime(2011, 02, 28), new DateTime(2011, 01, 30));
-1 = The Fisrt Date is Less than the Second
0 = The First Date is equal than the Second
1 = The First Date is Greater than the Second
DateTime objects are comparable themselves, so
if (dt1>dt2)
Console.WriteLine('dt1 is newer');
else if (dt1>dt2)
Console.WriteLine('dt2 is newer');
else // they are equal
Console.WriteLine('dt1 and dt2 are the same');
will work too.
In addition DateTime implements the IComparable<DateTime> interface, so you can do:
int result = dt1.CompareTo(dt2);
if (result > 0)
Console.WriteLine('dt1 is newer');
else if (result < 0)
Console.WriteLine('dt2 is newer');
else // result = 0
Console.WriteLine('dt1 and dt2 are the same');
EDIT: This ignores time zones, local times, etc...