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)
Related
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");
I have a string like that 03223311 (hhmmssff). I'm going to compare it with DateTime.Now and see if the difference between these to values is lower than 200 miliseconds.
xdate="03223311";
if(Math.Abs(Convert.ToInt32(xdate) - Convert.ToInt32(DateTime.Now.ToString("hhmmssff")))<200)
I tried to run the line above in a timer with interval of 1 but I can not reach to that condition even if I change xdate to current time... . Do you know how to solve the problem or even a better approach?
string input = "03223311";
var diff = DateTime.Now.TimeOfDay.Subtract(
TimeSpan.ParseExact(input, "hhmmssff", null)
).TotalMinutes; //or any other value like TotalMilliseconds
I would first convert the string into a DateTime so that you can compare apples to apples and utilized the features of the DateTime object. Once you have two DateTime objects, you can subtract them to get a TimeSpan. TimeSpan will have a TotalMilliseconds property that you can compare to your 200 constant.
var xdateValue = DateTime.ParseExact(xdate, "hhmmssff", CultureInfo.InvariantCulture);
var difference = DateTime.Now - xdateValue;
if (difference.TotalMilliseconds < 200) ...
if (((DatetTime.Now - DateTime.ParseExact("03223311 ", "hhmmssff", CultureInfo.InvariantCulture))).Milliseconds > 200)
{
}
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
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...
da = new SqlDataAdapter("SELECT ExitTime,EnterTime,name,[tag-id-st],[build-id],[room-no],tagType FROM Students,GateLogging WHERE GateLogging.tagType='student'", MyConn);
DateTime ss=dt.Rows[0][1];
DateTime date = DateTime.Now;
int x=date.CompareTo(ss);
This is my code, I stopped here and I can't complete
Please help me to compare the values in "EnterTime" table with the current time and show in gridview the values that is more than the current time with 10 minutes
First, find the date you actually care about - for example it might be
DateTime cutoff = DateTime.Now.AddMinutes(10);
(do this once at the top, rather than per row) - then just compare against those, for example:
bool isOverdue = ss > cutoff;
You can also do this inside the database with GETDATE() and DATEADD(...) or DATEDIFF(...)
First of all you can change the select query to return only rows for a last 10 minutes, and you will not need to compare, Second you can use da.Fill(dt) to copy resultset to datatable and use dt.Select("...") to filter only your rows, and the third what is the problem? you can write
DateTime now = DateTime.Now;
if (now - ss <= TimeSpan.FromMinutes(10))
{
}
Encountering the same problem in unit testing I wrote an AssertEx class with some less nitpicky assertions:
public static void AreSimilar(DateTime expected, DateTime actual, TimeSpan tolerance, string message)
{
DateTime expectedMin = expected.Subtract(tolerance);
DateTime expectedMax = expected.Add(tolerance);
if (actual < expectedMin || actual > expectedMax)
{
throw new AssertFailedException(message);
}
}