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Best way to Compare DateTime to trigger code

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");

C# can't compare two datetimes properly

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)

Get all months and years between two datetime

What I need is to get logic on how to get monthname-year between two dates.
Dictionary<Monthname,year> GetMonthsandYear(Datetime d1,Datetime d2)
or
List<Tuple<string,int> GetMonthsandYear(Datetime d1,Datetime d2)
example : jan-1-2013 to mar-3-2013
should return January-2013,february-2013,march-2013 or in reverse format by list.reverse

If your actual requirement is "the previous 24 months" then it's much simpler. Just start off with the current month, and get the 1st day of it - then iterate and add 1 month 24 times.
Personally I'd return an IEnumerable<DateTime> rather than anything else - you can format each element however you want - but it's pretty simple:
public static IEnumerable<DateTime> GetMonths(int count)
{
// Note: this uses the system local time zone. Are you sure that's what
// you want?
var today = DateTime.Today;
// Always return the 1st of the month, so we don't need to worry about
// what "March 30th - 1 month" means
var startOfMonth = new DateTime(today.Year, today.Month, 1);
for (int i = 0; i < count; i++)
{
yield return startOfMonth;
startOfMonth = startOfMonth.AddMonths(-1);
}
}
Then if you want a List<string> of these values as "February 2014" etc for example, you could have:
var monthYears = GetMonths(24).Select(dt => dt.ToString("MMMM yyyy"))
.ToList();
Note that a Dictionary<...> would not be appropriate unless you really don't care about the order - and I suspect you do. You shouldn't rely on the order in which items are returned from a Dictionary<TKey, TValue> when you view it as a sequence - it's not intended to be an ordered collection.

I don't understand why you need Dictionary or List<Tuple<string,int> but one solution could be;
DateTime dt1 = new DateTime(2013, 1, 1);
DateTime dt2 = new DateTime(2013, 3, 3);
while (dt1 < dt2)
{
Console.WriteLine(dt1.ToString("MMMM-yyyy"));
dt1 = dt1.AddMonths(1);
}
Result will be;
January-2013
February-2013
March-2013
Even if you need, you can add these values to a List<string> in while loop.
But be carefull about what Jon said, this solution will generate only January and February if your dt1.Day is greater than dt2.Day.

compare between dates in .net

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

Exact c# result of sql datediff

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