Develop Reference

Taking a DateTime value and only accepting time and vice versa

I'm currently developing an application to function as a todo - list and i was wondering how do i accept a Value from a date time box, but only use the value of the date, or the value of the time. I'm currently doing it like this.
DateTime ted = appointmentDateTimeDate.Value; //The date
DateTime at = appointmentDateTimeTime.Value; //The time
should i be doing this another way?

Use DateTime.Date property for date, and DateTime.TimeOfDay for time:
DateTime ted = appointmentDateTimeDate.Date; //The date
TimeSpan at = appointmentDateTimeTime.TimeOfDay; //The time

The BCL doesn't really separate dates and times nicely.
If you're happy to take a new external dependency, I'd like to plug my Noda Time library, which will let you separate things out clearly into LocalDate and LocalTime. To perform the conversion from a date/time picker you'd probably use:
var dateAndTime = LocalDateTime.FromDateTime(appointmentDateTimeDate.Value);
LocalDate date = dateAndTime.LocalDate;
LocalTime time = dateAndTime.LocalTime;

Like others pointed out a DateTime always has both a date and a time component. So although it's possible to save both independently using two DateTime, in most cases it's recommendable to save both together in a single DateTime instance.
You should see if you really need both values separated or if your application could combine both in one property, which will make things easier.

A DateTime value ALWAYS contains both the date and the time, whether you use both or not.
You can use the .Date property of a DateTime to get "just the date". it will still have a time value, but the time value will be midnight. You can also use the .TimeOfDay property to get the time portion, which will be a TimeSpan indicating the number of ticks since midnight.
I'm taking a leap here and assuming you're trying to set the date with one control an d the time with another in the UI. Here's a sample of some code we use to do this using an Ajax CalendarExtender attached to a textbox and a custom TimePicker control.
DateTime dt;
try
{
dt = Convert.ToDateTime(txtViewDate.Text).AddHours(txtViewTime.Hour).AddMinutes(txtViewTime.Minute);
if (txtViewTime.AmPm == MKB.TimePicker.TimeSelector.AmPmSpec.PM)
{
dt = dt.AddHours(12);
}
System.Diagnostics.Debug.WriteLine(dt.ToString());
}
catch (Exception)
{
// abort processing
return;
}

Create a date time with month and day only, no year

I am creating a timer job in VS for sharepoint, and I want to create a Date object that only has a month and day. The reason for this is because I want this job to run annually on the specific date.
If it's not possible with a date object, then how would you go about doing this?
Here's what I've got:
DateTime value = new DateTime(2010, 1, 18);

Well, you can create your own type - but a DateTime always has a full date and time. You can't even have "just a date" using DateTime - the closest you can come is to have a DateTime at midnight.
You could always ignore the year though - or take the current year:
// Consider whether you want DateTime.UtcNow.Year instead
DateTime value = new DateTime(DateTime.Now.Year, month, day);
To create your own type, you could always just embed a DateTime within a struct, and proxy on calls like AddDays etc:
public struct MonthDay : IEquatable<MonthDay>
{
private readonly DateTime dateTime;
public MonthDay(int month, int day)
{
dateTime = new DateTime(2000, month, day);
}
public MonthDay AddDays(int days)
{
DateTime added = dateTime.AddDays(days);
return new MonthDay(added.Month, added.Day);
}
// TODO: Implement interfaces, equality etc
}
Note that the year you choose affects the behaviour of the type - should Feb 29th be a valid month/day value or not? It depends on the year...
Personally I don't think I would create a type for this - instead I'd have a method to return "the next time the program should be run".

How about creating a timer with the next date?
In your timer callback you create the timer for the following year? DateTime has always a year value. What you want to express is a recurring time specification. This is another type which you would need to create.
DateTime is always represents a specific date and time but not a recurring date.

There is no such thing like a DateTime without a year!
From what I gather your design is a bit strange:
I would recommend storing a "start" (DateTime including year for the FIRST occurence) and a value which designates how to calculate the next event... this could be for example a TimeSpan or some custom structure esp. since "every year" can mean that the event occurs on a specific date and would not automatically be the same as saysing that it occurs in +365 days.
After the event occurs you calculate the next and store that etc.

Anyway you need 'Year'.
In some engineering fields, you have fixed day and month and year can be variable. But that day and month are important for beginning calculation without considering which year you are. Your user, for example, only should select a day and a month and providing year is up to you.
You can create a custom combobox using this: Customizable ComboBox Drop-Down.
1- In VS create a user control.
2- See the code in the link above for impelemnting that control.
3- Create another user control and place in it 31 button or label and above them place a label to show months.
4- Place the control in step 3 in your custom combobox.
5- Place the control in setp 4 in step 1.
You now have a control with only days and months. You can use any year that you have in your database or ....

Getting number of months based on days in c#

I'm stuck trying to figure this one out..
We currently have a date criteria on our reports, that are limited by days, configurable of course, currently set to 90 days.. message says, it is limited by 90 days, however my boss wants to increase it to 13 months, unfortunately if I did that, I'd need to do it by days and it would say, 395 days..
Not a very friendly message..
Trying to figure out a way to satisfy this, my other only option is to add another settings that is limited by months as well as days. but then i still need to convert the months back to days which wont be perfect since not every month has same days..
Ideas?

You need to decide if you're going to use 13 months as the time interval, or some number of days that approximates to 13 months. If you use 13 months, then the number of days (or the end date for your report) is going to vary depending on the start date.
I would suggest making your report configurable for either months or days (storing not just the number, but the units in configuration). You can then display on the report whatever has been specified in the configuration (with the units from configuration, too) and calculate the end date for the query by adding the configured number of configured units to the start date.
If you try to do everything in days, when you're now working in months, you'll just make life difficult for yourself.
It's much easier to add 13 months to the start date to get the end date, than it is to try and (inaccurately) work out how many months in a given number of days.

Use the TimeSpan object to perform the calculations you need for your date criteria.

I would do something like this, given the number of days:
int myDays; // 390 or whatever
DateTime d1 = DateTime.Now;
DateTime d2 = d1.AddDays(myDays);
int monthsDiff = d2.Month - d1.Month + 12 * (d2.Year - d1.Year);
DateTime d3 = d1.AddMonths(monthsDiff);
TimeSpan tf = d2 - d3;
string msg = monthsDiff.ToString() + " months, " + tf.Days + " days";

TimeSpan give you duration between two DateTime objects. It can give it consistently in Days, Hours or Mins; Number of months would be different based upon actual start & end dates as different months have different number of actual days.
Having said that, you can always write a Utility method that gives you YourTimeSpan object that gives you number of Months etc based upon your calendar and StartDate / EndDates.
In your case you can make it even simpler by storing it separately in configuration, for example - ReportDuration_Years, ReportDuration_Months, ReportDuration_Days. This would allow you to create meaningful lable on your report as well as allow to identify StartDate and EndDate properly.
//Call this by passing values from configuration
private string GetNiceLookingLable(int? years, int? months, int? days){
var yearMessage = (years.HasValue)?String.Format("{0} Years", years):String.Empty;
var monthMessage = (months.HasValue)?String.Format("{0} Months", months):String.Empty;
var daysMessage = (days.HasValue)?String.Format("{0} Days", days):String.Empty;
// You probably want to concatenate them properly
return String.Format("{0} {1} {2}",yearMessage, monthMessage, daysMessage);
}
-
//Call this to get starting date
private DateTime getStartingDate(int? years, int? months,int? days){
var retDate = DateTime.Today;
if(years.HasValue){
retDate = retDate.AddYears(-1*years.Value);
}
if(months.HasValue){
retDate = retDate.AddMonths(-1*months.Value);
}
if(days.HasValue){
retDate = retDate.AddDays(-1*days.Value);
}
return retDate;
}

Why is time coming as 0000 when i am using the todays date in C#

I am trying to create a string to show the current date and time without wanting to use any slashes just the numbers.
For example, 09 jun 2011 11AM should be 201109061100
But when i run the below code the time is always 0000
Output:
ResultLog201109060000
Code:
DateTime currDate = DateTime.Today;
String resultlogFilename;
resultlogFilename =
"ResultLog" +
currDate.ToString("yyyy") +
currDate.ToString("dd") +
currDate.ToString("MM") +
currDate.ToString("HH") +
currDate.ToString("mm");
Any idea how to get the correct time?

DateTime.Today seems to return the Date part not the hour part.
Just use DateTime.Now to get a complete time.
http://msdn.microsoft.com/en-us/library/system.datetime.now.aspx
Msdn DateTime.Today
Because it returns the current date without the current time, the Today property is suitable for use in applications that work with dates only. For details, see Choosing Between DateTime, DateTimeOffset, and TimeZoneInfo. In contrast, the TimeOfDay property returns the current time without the current date, and the Now property returns both the current date and the current time.

var resultlogFilename = string.Format("ResultLog{0:yyyyddMMhhmm}", DateTime.Now);

Use DateTime.Now instead of .Today. "Today" filters out the "time" part, so it effectively returns midnight (0:00).

It is because today returns to you only todays date and not todays time :)

Building a Datetime Object for SQL database insert

I'm working on a small web form that requires the user to input (among other things), the scheduled backup time of whatever server they're adding to the system. The problem is, I'm struggling to find out the best way to take the user input and build a DateTime object (which is what the database requires).
I only really care about the Day of Week, Time of Day (12 or 24 hour clock).
I thought about just creating an empty DateTime object and then just adding my input values from the user, but you can only get, not set, the day of week, time of day, etc.
I've been looking at the Calender asp control, which would work for the day of the week selection, but I can't seem to find any support of time of day.
Thanks.

I don't think you want to use a DateTime for a recurring event such as a backup. A DateTime is useful for storing a particular date and time, but not a "template" for a recurring event. Instead I'd use separate columns to store the day of week value (0-6) and time of date (minutes after midnight) for the event.

If you going to use datepicker here is one great sample for adding JQuery date picker using C#. That helped me including in my project evrn if I did know anything abaut JQuery and java sripts at all.

DateTime is a immutable value type. You cannot set anything on it.
Assumed that you stick with DateTime on the DB and you don't want to use a DateTimePicker control.
You have to specify how the day of week and the time should be represented in the DateTime. You can start with DateTime.MinValue, the 1.1.0001, 12:00 at midnight, and add the day of week and the time. unfortunately, a regular DateTime field in a SqlServer 2005 is not able to store this date. So lets move it to the year 2000. The 1.1.2000 was a Saturday. You could calculate the DateTime like this:
int dayOfWeek; // 0 = mon, 6 = son
DateTime time;
DateTime scheduleTime = new DateTime(2000, 1, (dayOfWeek + 2) % 6 + 1)
+ time.TimeOfDay;
But honestly, I wouldn't do it. It smells. I just answered your question. Listen to tvanfosson. He said everything that needs to be said.