Hello,

I have two nullable DateTime: begin and end.
I need to find the range, in month, between both variables.

If for some reason, for example begin is null, it is not possible to
calculate the range then I want to define the range as 1 month.

How can I do this?

Thanks,
Miguel

shapper wrote:
> I have two nullable DateTime: begin and end.
> I need to find the range, in month, between both variables.
>
> If for some reason, for example begin is null, it is not possible to
> calculate the range then I want to define the range as 1 month.
>
> How can I do this?

I don't think there are any magic.

if(dt1 != null && dt2 != null)
{
delta = (dt2 - dt1).TotalMonths;
}
else
{
delta = 1;
}

or something similar.

Arne

On Oct 18, 6:40*pm, Arne Vajhøj <a...@vajhoej.dk> wrote:
> shapper wrote:
> > I have two nullable DateTime: begin and end.
> > I need to find the range, in month, between both variables.
>
> > If for some reason, for example begin is null, it is not possible to
> > calculate the range then I want to define the range as 1 month.
>
> > How can I do this?
>
> I don't think there are any magic.
>
> if(dt1 != null && dt2 != null)
> {
> * * *delta = (dt2 - dt1).TotalMonths;}
>
> else
> {
> * * *delta = 1;
>
> }
>
> or something similar.
>
> Arne

In VB there is a really useful function named DateDiff. In C# there is
not ...

VisualBasic assembly could always be used but I prefer not to used
it ...

So I came up with the following:

int diff = 12 * (begin.Year - end.Year) + begin.Month - end.Month;
int months = Math.Abs(diff);

Not sure if it is the best option but I think I might implement a
DateDiff method for C#

On Oct 18, 8:03*pm, "Peter Duniho" <NpOeStPe...@nnowslpianmk.com>
wrote:
> On Sat, 18 Oct 2008 11:39:43 -0700, shapper <mdmo...@gmail.com> wrote:
> > In VB there is a really useful function named DateDiff. In C# there is
> > not ...
>
> In C# there is no need. *For that matter, DateDiff isn't really needed in *
> VB.NET. *It's there for legacy reasons.
>
> > VisualBasic assembly could always be used but I prefer not to used
> > it ...
>
> DateDiff doesn't address your original question. *Why would you bother to *
> try to use it?
>
> > So I came up with the following:
>
> > int diff = 12 * (begin.Year - end.Year) + begin.Month - end.Month;
> > int months = Math.Abs(diff);
>
> In what way does that address your original question?
>
> > Not sure if it is the best option but I think I might implement a
> > DateDiff method for C#
>
> Why? *What does DateDiff do for you that the operator- overload for *
> DateTime doesn't already?
>
> Pete

Sorry Pete,

But does not my code calculate the difference between two dates in
months?

int diff = 12 * (begin.Year - end.Year) + begin.Month - end.Month;
int months = Math.Abs(diff);

I didn't address the nullable DateTime yet.

DateDiff, in my opinion, just creates an "easier" way to calculate
datetime spans in various intervals ...

On Oct 18, 6:40*pm, Arne Vajhøj <a...@vajhoej.dk> wrote:
> shapper wrote:
> > I have two nullable DateTime: begin and end.
> > I need to find the range, in month, between both variables.
>
> > If for some reason, for example begin is null, it is not possible to
> > calculate the range then I want to define the range as 1 month.
>
> > How can I do this?
>
> I don't think there are any magic.
>
> if(dt1 != null && dt2 != null)
> {
> * * *delta = (dt2 - dt1).TotalMonths;}
>
> else
> {
> * * *delta = 1;
>
> }
>
> or something similar.
>
> Arne

Arne,

There isn't a TotalMonths in TimeSpan ... only TotalDays, TotalHours,
TotalSeconds, TotalMinutes and TotalMiliseconds.

That was the first thing I looked.

Thanks,
Miguel

On Oct 18, 8:17*pm, "Peter Duniho" <NpOeStPe...@nnowslpianmk.com>
wrote:
> On Sat, 18 Oct 2008 12:14:03 -0700, shapper <mdmo...@gmail.com> wrote:
> > But does not my code calculate the difference between two dates in
> > months?
>
> It does appear to, yes. *But so does the code that Arne posted. *And his *
> also addresses the specific question you actually asked. *More *
> importantly, your code has a whole lot of math in it, whereas just using *
> the already-overloaded operator- as Arne suggests, you let the DateTime *
> type do all the work for you.
>
> > int diff = 12 * (begin.Year - end.Year) + begin.Month - end.Month;
> > int months = Math.Abs(diff);
>
> > I didn't address the nullable DateTime yet.
>
> No, you didn't. *But that's actually the question you appeared to have *
> asked. *A solution that doesn't take into account null values isn't a *
> solution at all.
>
> > DateDiff, in my opinion, just creates an "easier" way to calculate
> > datetime spans in various intervals ...
>
> What could be easier that just subtracting one DateTime from another?
>
> Pete

Arne code does not solve it ... It is used TotalMonths which does not
exist in C#. I could use TotalDays / 30 but that wouldn't be accurate.
That is the reason of my code ...

Or maybe as follows:

public static long DateSpan(DateInterval interval, DateTime from,
DateTime to) {

// Define span
TimeSpan span = from - to;

// Check interval
switch (interval) {
case DateInterval.Year:
return to.Year - from.Year;
case DateInterval.Month:
return (to.Month - from.Month) + (12 * (to.Year -
from.Year));
case DateInterval.Weekday:
return CorrectDateSpan(span.TotalDays) / 7;
case DateInterval.Day:
return CorrectDateSpan(span.TotalDays);
case DateInterval.Hour:
return CorrectDateSpan(span.TotalHours);
case DateInterval.Minute:
return CorrectDateSpan(span.TotalMinutes);
default:
return CorrectDateSpan(span.TotalSeconds);
}

} // DateSpan

private static long CorrectDateSpan(double number) {

if (number >= 0) {
return (long)Math.Floor(number);
}
return (long)Math.Ceiling(number);

} // CorrectDateSpan

Note: Didn't tested it yet ...

This function would be a good help specially when I am using this on a
Linq query to define some statistics.

I could include on my function an option that when one of the dates is
null or if from is after to I would return null and then I could set a
default value on my code where I am using the function.

shapper wrote:
> On Oct 18, 6:40 pm, Arne Vajhøj <a...@vajhoej.dk> wrote:
>> shapper wrote:
>>> I have two nullable DateTime: begin and end.
>>> I need to find the range, in month, between both variables.
>>> If for some reason, for example begin is null, it is not possible to
>>> calculate the range then I want to define the range as 1 month.
>>> How can I do this?
>> I don't think there are any magic.
>>
>> if(dt1 != null && dt2 != null)
>> {
>> delta = (dt2 - dt1).TotalMonths;}
>>
>> else
>> {
>> delta = 1;
>>
>> }
>>
>> or something similar.

> There isn't a TotalMonths in TimeSpan ... only TotalDays, TotalHours,
> TotalSeconds, TotalMinutes and TotalMiliseconds.
>
> That was the first thing I looked.

Interesting.

It could be because TotalMonths is not very well defined.

Arne

shapper wrote:
> On Oct 18, 8:17 pm, "Peter Duniho" <NpOeStPe...@nnowslpianmk.com>
> wrote:
>> On Sat, 18 Oct 2008 12:14:03 -0700, shapper <mdmo...@gmail.com> wrote:
>>> But does not my code calculate the difference between two dates in
>>> months?
>> It does appear to, yes. But so does the code that Arne posted. And his
>> also addresses the specific question you actually asked. More
>> importantly, your code has a whole lot of math in it, whereas just using
>> the already-overloaded operator- as Arne suggests, you let the DateTime
>> type do all the work for you.
>>
>>> int diff = 12 * (begin.Year - end.Year) + begin.Month - end.Month;
>>> int months = Math.Abs(diff);
>>> I didn't address the nullable DateTime yet.
>> No, you didn't. But that's actually the question you appeared to have
>> asked. A solution that doesn't take into account null values isn't a
>> solution at all.
>>
>>> DateDiff, in my opinion, just creates an "easier" way to calculate
>>> datetime spans in various intervals ...
>> What could be easier that just subtracting one DateTime from another?
>
> Arne code does not solve it ... It is used TotalMonths which does not
> exist in C#.

Yep. Sorry about that.

> I could use TotalDays / 30 but that wouldn't be accurate.
> That is the reason of my code ...
>
> Or maybe as follows:
>
> public static long DateSpan(DateInterval interval, DateTime from,
> DateTime to) {
>
> // Define span
> TimeSpan span = from - to;
>
> // Check interval
> switch (interval) {
> case DateInterval.Year:
> return to.Year - from.Year;
> case DateInterval.Month:
> return (to.Month - from.Month) + (12 * (to.Year -
> from.Year));

If that is the business logic you want, then that is probably
the way to go.

It is not obvious though that there are 1 months between September
30th and Octobet 1st but 0 months between October 1st and October 31st.

Arne

On Oct 18, 8:41*pm, "Peter Duniho" <NpOeStPe...@nnowslpianmk.com>
wrote:
> On Sat, 18 Oct 2008 12:32:51 -0700, shapper <mdmo...@gmail.com> wrote:
> > Arne code does not solve it ... It is used TotalMonths which does not
> > exist in C#. I could use TotalDays / 30 but that wouldn't be accurate.
> > That is the reason of my code ...
>
> Ah, right. *Sorry. *I just assumed that Arne wouldn't post code that *
> doesn't compile; that's more like me to do that, not him. *
>
> And yes, you're right...no TotalMonths for TimeSpan. *Which actually makes *
> sense, now that I think about it, since TimeSpan is not relative to any *
> specific date, and the total months for a TimeSpan would depend on the *
> specific date.
>
> My recollection is that the System.Globalization.Calendar class has some *
> date/time math functionality in it. *Whether it addresses this specific*
> question, I'm not sure, and I don't have time to check at the moment. *But *
> you might look at that in the meantime.
>
> You could certainly write the basics yourself, especially if you have only *
> a very narrow need (for example, you always know you only need months). *
> But if there's something in the framework that accomplishes it, that's *
> probably better. *For that matter, if the Calendar class doesn't work, *
> maybe referencing the VB assembly is the best solution after all (but it *
> still won't deal with the nulls ...I really did read your original *
> question as being focused on the question of dealing with null values; I *
> didn't realize you were asking about the month calculation too).
>
> Pete

Thanks Pete. I will take a look into System.Globalization.Calendar.

On Oct 18, 8:42*pm, Arne Vajhøj <a...@vajhoej.dk> wrote:
> shapper wrote:
> > On Oct 18, 8:17 pm, "Peter Duniho" <NpOeStPe...@nnowslpianmk.com>
> > wrote:
> >> On Sat, 18 Oct 2008 12:14:03 -0700, shapper <mdmo...@gmail.com> wrote:
> >>> But does not my code calculate the difference between two dates in
> >>> months?
> >> It does appear to, yes. *But so does the code that Arne posted. *And his *
> >> also addresses the specific question you actually asked. *More *
> >> importantly, your code has a whole lot of math in it, whereas just using *
> >> the already-overloaded operator- as Arne suggests, you let the DateTime *
> >> type do all the work for you.
>
> >>> int diff = 12 * (begin.Year - end.Year) + begin.Month - end.Month;
> >>> int months = Math.Abs(diff);
> >>> I didn't address the nullable DateTime yet.
> >> No, you didn't. *But that's actually the question you appeared to have *
> >> asked. *A solution that doesn't take into account null values isn't a *
> >> solution at all.
>
> >>> DateDiff, in my opinion, just creates an "easier" way to calculate
> >>> datetime spans in various intervals ...
> >> What could be easier that just subtracting one DateTime from another?
>
> > Arne code does not solve it ... It is used TotalMonths which does not
> > exist in C#.
>
> Yep. Sorry about that.
>
>
>
> > * * * * * * *I could use TotalDays / 30 but that wouldn'tbe accurate.
> > That is the reason of my code ...
>
> > Or maybe as follows:
>
> > * * public static long DateSpan(DateInterval interval, DateTime from,
> > DateTime to) {
>
> > * * * // Define span
> > * * * TimeSpan span = from - to;
>
> > * * * // Check interval
> > * * * switch (interval) {
> > * * * * case DateInterval.Year:
> > * * * * * return to.Year - from.Year;
> > * * * * case DateInterval.Month:
> > * * * * * return (to.Month - from.Month) + (12 * (to.Year -
> > from.Year));
>
> If that is the business logic you want, then that is probably
> the way to go.
>
> It is not obvious though that there are 1 months between September
> 30th and Octobet 1st but 0 months between October 1st and October 31st.
>
> Arne

Yes, I didn't test it completely but I will check that. But has far as
I know that is also how it works in VB's DateDiff.