Example of C# method to implement DateTime class

In C#, the operations of date and time are mainly implemented through the class. DateTime provides a wealth of attributes and methods for processing date and time creation, formatting, comparison and calculation operations. Here are some commonly used date functions and features:

1. Creation date and time

1. Directly specify the date and time:

DateTime now = ; // Get the current date and timeDateTime today = ; // Get the current date (time part is 00:00:00)DateTime specificDate = new DateTime(2025, 2, 26, 14, 30, 0); // Specify the specific date and time

2. Parsing date and time from string:

DateTime parsedDate = ("2025-02-26 14:30:00"); // parse from standard format stringDateTime parsedDateWithFormat = ("26/02/2025 14:30", "dd/MM/yyyy HH:mm", null); // Use custom format to parse

2. Obtain the components of date and time

DateTime provides multiple read-only properties to get the various parts of the date and time:

Year : Get the year.
Month : Get the month (1-12).
Day : Get the date (1-31).
Hour : Get hours (0-23).
Minute : Get minutes (0-59).
Second : Get seconds (0-59).

Example:

DateTime now = ;
($"Year: {}, Month: {}, Day: {}");
($"Hour: {}, Minute: {}, Second: {}");

3. Calculation of date and time

1. Addition and subtraction date and time:

DateTime now = ;
DateTime tomorrow = (1); // Add 1 dayDateTime yesterday = (-1); // 1 day offDateTime nextWeek = (1); // Add 1 week (requires an extension method)DateTime nextHour = (1); // Add 1 hour

2. Calculate the difference between two dates:

DateTime date1 = new DateTime(2025, 2, 26);
DateTime date2 = new DateTime(2025, 3, 1);
TimeSpan difference = date2 - date1; // Return the TimeSpan object($"Days: {}, Hours: {}");

4. Format date and time

1. Standard formatting:

DateTime now = ;
string formattedDate = ("yyyy-MM-dd HH:mm:ss"); // Custom formatstring shortDate = (); // Short date format (such as: 2025/02/26)string longDate = (); // Long date format (such as: February 26, 2025)

2. Custom formatting:

string customFormat = ("dd/MM/yyyy HH:mm:ss tt"); // Custom format (such as: 26/02/2025 14:30:00 PM)

5. Comparison of dates and time

1. Compare two dates:

DateTime date1 = new DateTime(2025, 2, 26);
DateTime date2 = new DateTime(2025, 3, 1);

if (date1 < date2)
{
    ("date1 is earlier than date2");
}
else if (date1 > date2)
{
    ("date1 is later than date2");
}
else
{
    ("date1 is the same as date2");
}

2. Judge date range:

DateTime start = new DateTime(2025, 2, 1);
DateTime end = new DateTime(2025, 2, 28);
DateTime testDate = new DateTime(2025, 2, 15);

if (testDate >= start && testDate <= end)
{
    ("testDate is within the range");
}

6. Other common methods

1. Determine whether it is a leap year:

bool isLeapYear = (2024); // Return true

2. Get the day of the week:

DateTime now = ;
string dayOfWeek = (); // Return to the day of the week (such as Wednesday)

7. Expansion method

C# allows adding custom functions to DateTime through extension methods. For example, add an AddWeeks method:

public static class DateTimeExtensions
{
    public static DateTime AddWeeks(this DateTime date, int weeks)
    {
        return (weeks * 7);
    }
}

// useDateTime now = ;
DateTime nextMonth = (4);

Summarize

It is the core structure for processing dates and time in C#, providing rich functions to meet the needs of most date and time operations. By combining DateTime and TimeSpan, date calculation, formatting and comparison operations can be easily implemented.

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