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Visual C# Guide
The DateTime Structure
There are lots of situations where it necessary for programmers to wok with dates or times. The DateTime structure contains many properties and methods to make this easier.
When you declare a variable of the type DateTime, it represents an instant in time, normally expressed as a date and time of day.
For example,
DateTime now = DateTime.Today;
Console.WriteLine("Today's date is {0} ",now);
DateTime currTimeAndDate = DateTime.Now;
Console.WriteLine("The curent date and time is {0}", currTimeAndDate);
DateTime tomorrow = currTimeAndDate.AddDays(1);
Console.WriteLine("Tomorrow it will be {0} ", tomorrow);
DateTime then = new DateTime(2000,1,1);
Console.WriteLine("The first day of 2000 was {0}", then.DayOfWeek);
Console.ReadLine();
Type in and run the program above. Adapt the program to tell you what the day of the week was when you were born.
Creating A New DateTime
The constructor function for the DateTime structure is overloaded. This means that there are multiple ways to create DateTimes. You are most likely to use the following,
DateTime myDate = New DateTime(year, month, day);
DateTime myDateTime = New DateTime(year, month, day, hour, minute, second);
DateTime Properties
The following properties are used to create and manipulate instances of DateTime structure.
| Property | Description | Type |
| Date | Gets the date component | DateTime |
| Day | Gets the day component | Integer |
| DayOfWeek | Gets the week day | DayOfWeek Enumeration |
| Hour | Gets the hour component | Integer |
| Millisecond | Gets the millisecond component | Integer |
| Minute | Gets the minute component | Integer |
| Month | Gets the month component | Integer |
| Now | Gets a DateTime object that is the current date and time | DateTime |
| Second | Gets the second component | Integer |
| TimeOfDay | Gets the time part of a DateTime instance | TimeSpan |
| Today | Gets a DateTime object that is the current date and time set to 00:00:00 | DateTime |
| Year | Gets the year component | Integer |
DateTime Methods
The following methods can be used to manipulate a DateTime instance. Look at how some of these are used in the example above.
| Method | Description |
| AddDays(d) | Adds d days to the DateTime |
| AddHours(h) | Adds h hours to the DateTime |
| AddMilliseconds(m) | Adds m milliseconds to the DateTime |
| AddMinutes(m) | Adds m minutes to the DateTime |
| AddMonths(m) | Adds m months to the DateTime |
| AddSeconds(s) | Adds s seconds to the DateTime |
| AddYears(y) | Adds y years to the DateTime |
| DaysInMonth(y, m) | Returns an integer equal to the number of days in month m of year y. |
| IsLeapYear(y) | Returns a Boolean (true or false) |
| ToShortDateString() | Returns a short string representation of the date component of a DateTime |
| ToShortTimeString() | Returns a short string representation of the time component of a DateTime |
| ToString() | Returns a string representation of a DateTime |
Having A Go
- Write a program that allows the user to type in a date and get the day of the week for that date.
- Write a program that tells the user whether a year entered at the keyboard is a leap year.