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C# Object-Oriented (OOP)

C# Date and Time (DateTime)

C# includes the DateTime structure that can handle dates and times.

To use date and time in C#, use the new keyword to create an object of the DateTime structure. Below, create a DateTime object with a default value.

Example: Create DateTime object

DateTime dt = new DateTime();　//　Assign default value 01/01/0001　00:00:00

The default value and minimum value of DateTime objects are 0001Year1Month1Day 00:00:00 (midnight). The maximum value can be9999Year12Month31Night11:59:59

Use different constructors of the DateTime structure to assign initial values to DateTime objects.

Example: Set date and time

//Assign default value 01/01/0001　00:00:00
DateTime dt1　= new DateTime();　
//Assign year, month, day
DateTime dt2　= new DateTime(2015,　12,　31);　
//Assign year, month, day, hour, min, seconds
DateTime dt3　= new DateTime(2015,　12,　31,　5,　10,　20);
　
//Assign year, month, day, hour, min, seconds, UTC timezone
DateTime dt4　= new DateTime(2015,　12,　31,　5,　10,　2, DateTimeKind.Utc);

In the above example, we specify the year, month, and day in the constructor. The year can be 0001To9999, the month can be1To12, the date can be1To31. Setting any other value outside these ranges will cause a runtime exception.

Example: Invalid date

DateTime dt = new DateTime(2015,　12,　32);　//Raises an exception: Day out of range

Use different DateTime constructors to set date, time, time zone, calendar, and regionality.

Ticks

Ticks is a date and time starting from the Gregorian calendar 00:00:00.000 year1Month1Since the day100 nanoseconds interval count. Below, initialize a DateTime object with the scale number.

Example: Ticks

DateTime dt = new DateTime(636370000000000000);　
DateTime.MinValue.Ticks;　　//Minimum value
DateTime.MaxValue.Ticks;　//　Maximum value

DateTime static fields

The DateTime structure includes static fields, properties, and methods. The following examples demonstrate important static fields and properties.

Example: Electrostatic field

DateTime currentDateTime = DateTime.Now;　　//Return the current date and time
DateTime todaysDate = DateTime.Today;　//　Return today's date
DateTime currentDateTimeUTC = DateTime.UtcNow;//　Return the current UTC date and time
DateTime maxDateTimeValue = DateTime.MaxValue;　//　Return the maximum value of DateTime
DateTime minDateTimeValue = DateTime.MinValue;　//　Returns the minimum value of DateTime

TimeSpan (time span)

TimeSpan is a structure used to represent time in days, hours, minutes, seconds, and milliseconds.

Example: TimeSpan

DateTime dt = new DateTime(2015,　12,　31);
　　　　　　　　　　　
TimeSpan ts = new TimeSpan(25,20,55);
　
DateTime newDate = dt.Add(ts);
Console.WriteLine(newDate);//1/1/2016　1:20:55　AM

Subtracting two dates results in a TimeSpan.

Example: Subtracting dates

DateTime dt1　= new DateTime(2015,　12,　31);　
DateTime dt2　= new DateTime(2016,　2,　2);
TimeSpan result = dt2.Subtract(dt1);//33.00:00:00

operators

DateTime structure overloads+,-The == != > < <= >= operators simplify the addition, subtraction, and comparison of dates. These make it easy to handle dates.

Example: Operators

DateTime dt1　= new DateTime(2015,　12,　20);
DateTime dt2　= new DateTime(2016,　12,　31,　5,　10,　20);　
TimeSpan time = new TimeSpan(10,　5,　25,　50);
Console.WriteLine(dt2　+　time);　//　1/10/2017Morning10:36:10
Console.WriteLine(dt2　-　dt1);　//377.05:10:20
Console.WriteLine(dt1　== dt2);　//False
Console.WriteLine(dt1　!= dt2);　//True
Console.WriteLine(dt1　> dt2);　//False
Console.WriteLine(dt1　< dt2);　//True
Console.WriteLine(dt1　>= dt2);　//False
Console.WriteLine(dt1　<= dt2);//True

Convert DateTime to String

The DateTime structure contains the following methods to convert dates and times to strings.

Method	Description
ToString	Convert DateTime value to a string in a specified format in the current region.
ToShortDateString	Convert DateTime value to short date string in the current region (M/d/yyyy format).
ToShortTimeString	Convert DateTime value to short time string in the current region (h: mm: ss format).
ToLongDateString	Convert DateTime value to long date string in the current region (dddd, MMMM d, yyyy format).
ToLongTimeString	Convert DateTime value to long time string in the current region (h:mm:ss tt format).

The following example demonstrates how to convert DateTime to different string formats.

Example: DateTime to String

var dt = DateTime.Now;
Console.WriteLine("Date String Current Culture: ");　+　dt.ToString("d"));
Console.WriteLine("MM/dd/yyyy Format:");　+　dt.ToString("MM/dd/yyyy"));
Console.WriteLine("dddd, dd MMMM yyyy Format:");　+　dt.ToString("dddd, dd MMMM yyyy"));
Console.WriteLine("MM/dd/yyyy h:mm tt Format:");　+　dt.ToString("MM/dd/yyyy h:mm tt"));
Console.WriteLine("MMMM dd Format:");　+　dt.ToString("MMMM dd"));
Console.WriteLine("HH:mm:ss Format:");　+　dt.ToString("HH:mm:ss"));
Console.WriteLine("hh:mm tt Format:");　+　dt.ToString("hh:mm tt"));
Console.WriteLine("Short Date String: ");　+　dt.ToShortDateString());
Console.WriteLine("Long Date String: ");　+　dt.ToLongDateString());
Console.WriteLine("Short Time String: ");　+　dt.ToShortTimeString());
Console.WriteLine("Long Time String: ");　+　dt.ToLongTimeString());

Convert string to DateTime

The Parse (), ParseExact (), TryParse (), and TryParseExact () methods can be used to convert valid date and time string to DateTime object.

If the specified string is not a valid representation of a date and time, the Parse () and ParseExact () methods will throw an exception. Therefore, it is recommended to use TryParse () or TryParseExact () methods, as they will return false if the string is invalid.

Example:

var str = "5/12/2020";
DateTime dt;
　　　　　　　　　　　　
var isValidDate = DateTime.TryParse(str, out dt);
if(isValidDate)
　　　　Console.WriteLine(dt);
else
　　　　Console.WriteLine($"{str} is not a valid date string");

C# FileInfo C# Strings (String)