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Finding if the two DateTime is within a week

I wanted to find if two DateTime are within a week.
One of them is the current system Datetime, which I got it by using:
DateTime CurrentDateTime = new DateTime();
CurrentDateTime = DateTime.Now;
The other DateTime will just be a selected date. Assuming it is stored in a variable called : ExportDate.
So, I can find the difference between them by doing
ExportDate.Subtract(CurrentDateTime)
But I cannot change this value into a int for comparing...
So how should I compare this to DateTime to see if this two dates are greater then 0Days, and less then 7Days.

Subtracting two datetimes gives you a TimeSpan. This class comes with a property called TotalDays.
Gets the value of the current TimeSpan structure expressed in whole and fractional days.
Src: https://msdn.microsoft.com/en-Us/library/system.timespan(v=vs.110).aspx
You can use to count the number of days I guess.
Regards,
Seb

Try to compare the TotalDays of the resulting TimeSpan. Depending on which is later, the result must be between -7 and 7. Use Math.Abs to avoid comparing the value against both bounds:
bool isWithinWeek = Math.Abs(ExportDate - CurrentDate).TotalDays) < 7
If the time of day is irrelevant, compare only the dates:
bool isWithinWeek = Math.Abs(ExportDate.Date - CurrentDate.Date).TotalDays) < 7

You can use
(ExportDate - CurrentDateTime).TotalDays <= 7

You can simply use the DayOfYear property of DateTime to get the day in the year and then check if the difference is less than 7 or not. You can try:
bool isWithinAWeek = Math.Abs(currentDateTime.DayOfYear-exportDate.DayOfYear)>7?false:true;

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");

Subtracting timespan from 24 hours

I'm trying to subtract my potentially negative timespan values from 24 hours to change them into positive values.
As an example case:
I want to find how much time is there till 8:00 AM.
If it's 16:00 PM now, timespan gives me -8 ish value so I want to substract it from 24 to get 16.
I'm trying this but it's giving me this error
The DateTime represented by the string is not supported in calendar
System.Globalization.GregorianCalendar.
What I tried ;
string startTime = String.Format("{0:t}", "8:00");
TimeSpan timeLeft = Convert.ToDateTime(startTime).Subtract(DateTime.Now);
if (timeLeft.TotalMinutes < 0 )
{
timeLeft = Convert.ToDateTime(String.Format("{0:H}","24:00")).Subtract(Convert.ToDateTime(timeLeft.Negate())) ;
}
How can I achieve subtracting my potentially negative timespans from 24 hours?

You are confusing TimeSpan and DateTime. I guess there is an easier way:
var eightOClock = TimeSpan.FromHours(8);
var now = DateTime.Now;
var till8again = now.TimeOfDay > eightOClock
? TimeSpan.FromHours(32) - now.TimeOfDay
: eightOClock - now.TimeOfDay;
So if TimeOfDay is less than eight hours (it's before 8am), we take the difference to 8am. If it's greater than 8am, we take the difference to 32hours, which is 8am tomorrow.

A DateTime is an absolute date, happening at a certain day, month, year... It must not be used to represent a specific hour.
So your attempt to convert "8:00", or "24:00" in a DateTime will forcibly fail.
For this you must use TimeSpan (or eventually an integer if you always work with hours).
You can use for example
if(DateTime.Now.TimeOfDay > TimeSpan.FromHours(8))
To see if it's more or less than 8:00.
TimeOfDay will return you the amount of time elapsed for today since midnight.
DateTime has also a lot of useful methods to Add or Substract time, see https://msdn.microsoft.com/fr-fr/library/system.datetime(v=vs.110).aspx for details

Use TimeSpan, and if the startDate is less the Now, add a day to it and then make the comparison.
TimeSpan startTime = new TimeSpan(8,0,0);
TimeSpan now = DateTime.Now.TimeOfDay;
startTime = startTime < now ? startTime.Add(TimeSpan.FromDays(1)) : startTime;
TimeSpan diff = startTime - now;

Another point: the error is coming from the fact that 24:00 doesn't represent 12:00 midnight. 0:00 represents midnight, and that will be a valid DateTime.

How do I disregard the time portion when comparing two date values?

I want this to equate to false when the date displayed is today's date:
if (dateTimePickerScheduleDate.Value < DateTime.Now)
...but it doesn't, because the DTP's value contains "midnight" whereas "Now" is after midnight.
How do I "trunc" these values so that it disregards the time portion?

if(dateTimePickerScheduleDate.Value.Date < DateTime.Now.Date)
{
}
The Date property returns a DateTime reflecting only the Date component of your DateTime object with its time component zero'ed out.

DateTime.Now.ToShortDateString();

Regular DateTime question

I'm writing a service but I want to have config settings to make sure that the service does not run within a certain time window on one day of the week. eg Mondays between 17:00 and 19:00.
Is it possible to create a datetime that represents any monday so I can have one App config key for DontProcessStartTime and one for DontProcessEndTime with a values like "Monday 17:00" and "Monday 19:00"?
Otherwise I assume I'll have to have separate keys for the day and time for start and end of the time window.
Any thoughts?
thanks

You could use a utility that will parse your weekday text into a System.DayOfWeek enumeration, example here. You can then use the Enum in a comparison against the DateTime.Now.DayOfWeek

You can save the day of the week and start hour and endhour in your config file, and then use a function similar to the following:
public bool ShouldRun(DateTime dateToCheck)
{
//These should be read from your config file:
var day = DayOfWeek.Monday;
var start = 17;
var end = 19;
return !dateToCheck.DayOfWeek == day &&
!(dateToCheck.Hour >= start && dateToCheck.Hour < end);
}

You can use DayOfTheWeek property of the DateTime.
And to check proper time you can use DateTime.Today (returns date-time set to today with time set to 00:00:00) and add to it necessary amount of hours and minutes.

The DateTime object cannot handle a value that means all mondays. It would have to be a specific Monday. There is a DayOfWeek enumeration. Another object that may help you is a TimeSpan object. You could use the DayOfWeek combined with TimeSpan to tell you when to start, then use another TimeSpan to tell you how long

This is very rough code, but illustrates that you can check a DateTime object containing the current time as you wish to do:
protected bool IsOkToRunNow()
{
bool result = false;
DateTime currentTime = DateTime.Now;
if (currentTime.DayOfWeek != DayOfWeek.Monday && (currentTime.Hour <= 17 || currentTime.Hour >= 19))
{
result = true;
}
return result;
}