Develop Reference

How to select weekends with an interval between them?

How can I select all weekends until the end of the year, with some criteria to be followed?
User input desired Weekend day:
18/12/2021
Software must out:
25/12/2022 (must be ignored)
01/01/2022
08/01/2022 (must be ignored)
15/01/2022
22/01/2022 (must be ignored)
29/01/2022 and so on...
What i have now:
public void GetWeekends() {
var lastWorkedWeekend = dateTimePicker1.Value;
var workedInSunday = checkBox1.Checked;
var list = new List < DateTime > ();
var weekends = GetDaysBetween(lastWorkedWeekend, DateTime.Today.AddDays(365)).Where(d => d.DayOfWeek == DayOfWeek.Saturday);
var selected = true;
for (int i = 0; i < weekends.Count(); i++) {
if (selected == false) {
list.Add(weekends.ElementAt(i));
selected = true;
} else {
selected = false;
}
}
}

I think I'd just scroll the input day forward until it was saturday (or calculate it, but i find the loop more self documenting than casting DayOfWeek to an int and factoring for sunday being 0) then add 14 days repeatedly. This skips over the 25th, etc..
var d = new DateTime(2021, 12, 18);
while(d.DayOfWeek != DayOfWeek.Saturday)
d += TimeSpan.FromDays(1);
while(d.Year == 2021){ //was your 2022 a typo? or maybe make this <= 2022.. I'm not sure what you want there..
d += TimeSpan.FromDays(14);
Console.WriteLine(d);
}
You might prefer DateTime.AddDays()..

Looks to me that you want to get the date of every second weekend from an initial date until the end of the year. In your example, you kinda bleed over to the next year.
public static void Main()
{
var dates = GetDateTimeRange(new DateTime(2021, 12, 18), new DateTime(2023, 1, 1), TimeSpan.FromDays(14));
foreach (var dateTime in dates.Skip(1))
{
Console.WriteLine(dateTime);
}
}
public static IEnumerable<DateTime> GetDateTimeRange(DateTime startingDate, DateTime endDate, TimeSpan interval)
{
var lastDate = startingDate;
while (lastDate < endDate)
{
yield return lastDate;
lastDate = lastDate.Add(interval);
}
}
This returns
01/01/2022 00:00:00
01/15/2022 00:00:00
01/29/2022 00:00:00
02/12/2022 00:00:00
02/26/2022 00:00:00
03/12/2022 00:00:00
03/26/2022 00:00:00
04/09/2022 00:00:00
04/23/2022 00:00:00
05/07/2022 00:00:00
05/21/2022 00:00:00
06/04/2022 00:00:00
06/18/2022 00:00:00
07/02/2022 00:00:00
07/16/2022 00:00:00
07/30/2022 00:00:00
08/13/2022 00:00:00
08/27/2022 00:00:00
09/10/2022 00:00:00
09/24/2022 00:00:00
10/08/2022 00:00:00
10/22/2022 00:00:00
11/05/2022 00:00:00
11/19/2022 00:00:00
12/03/2022 00:00:00
12/17/2022 00:00:00
12/31/2022 00:00:00

One approach is to use a method that creates an enumerable of dates. Once that's done you can use LINQ queries. If creating that enumerable is expensive you could just create one large range encompassing years and re-use it.
Or you might find better performance by just creating the range you need for each query.
public static class DateRanges
{
public static IEnumerable<DateOnly> GetRange(DateOnly start, DateOnly end)
{
for (var date = start; date <= end; date = date.AddDays(1))
{
yield return date;
}
}
}
It's not clear from your code what the criteria is, but this does what you described - all weekends from now to the end of the year.
var today = DateOnly.FromDateTime(DateTime.Today);
var lastDayOfYear = DateOnly.FromDateTime(new DateTime(DateTime.Today.Year, 12, 31));
var dates = DateRanges.GetRange(today, lastDayOfYear);
var weekendsOnly = dates.Where(date =>
date.DayOfWeek == DayOfWeek.Saturday);
Or if you prefer to create one date range and query it repeatedly:
// Big range of dates, 10 years into past and future.
// Create this once and re-use it
var dates = DateRanges.GetRange(
DateOnly.FromDateTime(DateTime.Today.AddYears(-10)),
DateOnly.FromDateTime(DateTime.Today.AddYears(10)));
var today = DateOnly.FromDateTime(DateTime.Today);
var lastDayOfYear = DateOnly.FromDateTime(new DateTime(DateTime.Today.Year, 12, 31));
var weekendsOnly = dates.Where(date =>
date >= today
&& date <= lastDayOfYear
&& date.DayOfWeek == DayOfWeek.Saturday);
In either case if you want every other Saturday you can add
.Where((date, i) => i % 2 == 0);
Or to maintain that readability you could put that in another extension like
public static IEnumerable<T> EveryOther<T>(this IEnumerable<T> source)
{
return source.Where((date, i) => i % 2 == 0);
}
so your query looks like
var everyOtherWeekend = dates
.Where(date =>
date >= today
&& date <= lastDayOfYear
&& date.DayOfWeek == DayOfWeek.Saturday)
.EveryOther();
I wouldn't position this as a better answer than those that iterate over a series of dates. The difference is that instead of having to write a method for any query you can start with a range of dates and then use LINQ to filter it. That makes it a little easier to read and to compose different queries.

how to get the get first Sunday of the month using date format?

Hi I need to check a condition for the first Sunday of the month for a date formatted as YYYYMMDD
var calDate = data.value; // example 20210502 is sunday
if (first Sunday of the month)
{
do this
}
else
{
do that
}
I need to check the above condition for the first Sunday of the month

Split your problem in two:
parse the string to a DateTime object
var date = DateTime.ParseExact(calDate, "yyyyMMdd", null);
Check if the DateTime object refers to the first sunday in a month. For this, it must obviously be a Sunday and the day part must be in the range 1 to 7:
var isFirstSunday = date.DayOfWeek == DayOfWeek.Sunday && date.Day <= 7;

Thsi function can return true or false if the date is first Sunday of the month or not
private static bool IsFirstSunday(DateTime date)
{
int i = 1;
while (i!=7)
{
if (date.Day==i && date.DayOfWeek == DayOfWeek.Sunday)
{
return true;
}
i++;
}
return false;
}
And use the result in your if condition
//First sunday
var date = DateTime.Parse("2021-05-02 11:27 AM");
var result = IsFirstSunday(date);
//Second sunday
date = DateTime.Parse("2021-05-09 11:27 AM");
result = IsFirstSunday(date);
//Non sunday
date = DateTime.Parse("2021-05-04 11:27 AM");
result = IsFirstSunday(date);

public static DateTime GetFirstSundayOfMonth(DateTime givenDate)
{
DateTime firstDayNextMonth = givenDate.AddDays(-givenDate.Day + 1).AddMonths(1);
int diff = 7 - (int)firstDayNextMonth.DayOfWeek;
return firstDayNextMonth.AddDays(diff);
}

Getting last 7 days data from days name like sunday, monday, tuesday etc in linq asp.net mvc

I want to fetch data by last week days like last Sunday, last Monday and so on 7 days. I wrote this query but I returns null.
var dateCriteria = DateTime.Now.Date.AddDays(-7);
var one = _context.Sale.Where(m => m.Date >= dateCriteria && m.Date.DayOfWeek.ToString() ==
"Sunday");

DayOfWeek is enum. So just use it without conversion:
var dateCriteria = DateTime.Now.Date.AddDays(-7);
var one = _context.Sale.Where(m => m.Date >= dateCriteria && m.Date.DayOfWeek ==
DayOfWeek.Sunday);

I am not sure if I understood your question correctly but here is what I would do to get the last Sunday's sales.
var one = _context.Sale.Where(m => m.Date == GetLast(DayOfWeek.Sunday));
private DateTime GetLast(DayOfWeek dayOfWeek) {
var currentDate = DateTime.Now.Date;
var currentDayOfWeek = (int)currentDate.DayOfWeek;
if (currentDayOfWeek <= (int)dayOfWeek) {
currentDayOfWeek = currentDayOfWeek + 7;
}
int daysToExtract = currentDayOfWeek - (int)dayOfWeek;
return currentDate.AddDays(-daysToExtract);
}

How to return a list of weekend dates between 2 dates

At the moment I have this code to return a table of all dates between 2 dates. How could I change this to have it only return the weekend dates.
The purpose of this is to use the weekend dates to check against column headers in a DataGridView to "grey-out" the weekends. I hope that's clear.
static public List<string> GetDates(DateTime start_date, DateTime end_date)
{
List<string> days_list = new List<string>();
for (DateTime date = start_date; date <= end_date; date = date.AddDays(1))
{
days_list.Add(date.ToShortDateString());
}
return days_list;
}

Use the DateTime.DayOfWeek property.
https://msdn.microsoft.com/en-US/library/system.datetime.dayofweek(v=vs.110).aspx
static public List<string> GetDates(DateTime start_date, DateTime end_date)
{
List<string> days_list = new List<string>();
for (DateTime date = start_date; date <= end_date; date = date.AddDays(1))
{
if (date.DayOfWeek == DayOfWeek.Sunday || date.DayOfWeek == DayOfWeek.Saturday)
days_list.Add(date.ToShortDateString());
}
return days_list;

You can create range of dates and then filter on them using DayOfWeek as #Vitor said:
static public List<DateTime> GetWeekendDates(DateTime start_date, DateTime end_date)
{
return Enumerable.Range(0, (int)((end_date- start_date).TotalDays) + 1)
.Select(n => StartDate.AddDays(n))
.Where(x=>x.DayOfWeek == DayOfWeek.Saturday
|| x.DayOfWeek == DayOfWeek.Sunday)
.ToList();
}

hope this solution will help you
DateTime startDate = new DateTime(2011,3,1);
DateTime endDate = DateTime.Now;
TimeSpan diff = endDate - startDate;
int days = diff.Days;
for (var i = 0; i <= days; i++)
{
var testDate = startDate.AddDays(i);
switch (testDate.DayOfWeek)
{
case DayOfWeek.Saturday:
case DayOfWeek.Sunday:
Console.WriteLine(testDate.ToShortDateString());
break;
}
}
in above code I am finding Saturday and Sunday between 1st March 2011 and today. So I have taken two variables called startDate and endDate. After that I have got difference between them and then via for loop I am checking that day of week is Saturday or Sunday

How do I determine if a date lies between current week dates?

In C#,
How we are check certain date with in week dates?
Eg: 6/02/2014
Current Weeks: 02/02/2014 - 08/02/2014
so this dates are with in above week....

Use this for check (last parameter is optional if you want always 1 week from fromDate, you don't need use last parameter):
public static bool DateInside(DateTime checkDate,
DateTime fromDate, DateTime? lastDate = null)
{
DateTime toDate = lastDate != null ? lastDate.Value : fromDate.AddDays(6d);
return checkDate >= fromDate && checkDate <= toDate;
}
To call use:
bool isDateInside = DateInside(new DateTime(2014, 02, 06),
new DateTime(2014, 02, 02)); // return true
And search first :) Answer is also here: How to check whether C# DateTime is within a range
If you want to check if the dates are inside the same week, then you can use this:
public static bool DateInsideOneWeek(DateTime checkDate, DateTime referenceDate)
{
// get first day of week from your actual culture info,
DayOfWeek firstWeekDay = System.Globalization.CultureInfo.CurrentCulture.DateTimeFormat.FirstDayOfWeek;
// or you can set exactly what you want: firstWeekDay = DayOfWeek.Monday;
// calculate first day of week from your reference date
DateTime startDateOfWeek = referenceDate;
while(startDateOfWeek.DayOfWeek != firstWeekDay)
{ startDateOfWeek = startDateOfWeek.AddDays(-1d); }
// fist day of week is find, then find last day of reference week
DateTime endDateOfWeek = startDateOfWeek.AddDays(6d);
// and check if checkDate is inside this period
return checkDate >= startDateOfWeek && checkDate <= endDateOfWeek;
}
Actual week in my culture info start with monday, February 3th 2014 (so for me is week between February 3th and February 9th). If I check any date with reference date (second parameter) as today (2014-Feb-06) I get this results:
For 2014-Feb-02 (Sunday before this week): false
For 2014-Feb-03 (Monday inside this week): true
For 2014-Feb-06 (Today inside this week): true
For 2014-Feb-09 (Sunday inside this week): true
For 2014-Feb-10 (Monday next week): false
You can call this method to check if one date is inside the same week as referentional like this:
DateInsideOneWeek(new DateTime(2014, 02, 02), new DateTime(2014, 02, 06));
You can find current week start and end dates with this code:
DateTime startDateOfWeek = DateTime.Now.Date; // start with actual date
while(startDateOfWeek.DayOfWeek != DayOfWeek.Monday) // set first day of week in your country
{ startDateOfWeek = startDateOfWeek.AddDays(-1d); } // after this while loop you get first day of actual week
DateTime endDateOfWeek = startDateOfWeek.AddDays(6d); // you just find last week day
Is this you wanted?

hmm
public bool isBetween(DateTime input, DateTime date1, DateTime date2)
{
if (input > date1 && input < date2)
return true;
else
return false;
}
?
input= your date
date1 & date2 = start and end of a week

How about:
bool inRange = (date >= lowerDate && date <= upperDate);

Here's another solution :)
public static class DateExtensions
{
private static void Swap<T>(ref T one, ref T two)
{
var temp = one;
one = two;
two = temp;
}
public static bool IsFromSameWeek(this DateTime first, DateTime second, DayOfWeek firstDayOfWeek = DayOfWeek.Monday)
{
// sort dates
if (first > second)
{
Swap(ref first, ref second);
}
var daysDiff = (second - first).TotalDays;
if (daysDiff >= 7)
{
return false;
}
const int TotalDaysInWeek = 7;
var adjustedDayOfWeekFirst = (int)first.DayOfWeek + (first.DayOfWeek < firstDayOfWeek ? TotalDaysInWeek : 0);
var adjustedDayOfWeekSecond = (int)second.DayOfWeek + (second.DayOfWeek < firstDayOfWeek ? TotalDaysInWeek : 0);
return adjustedDayOfWeekSecond >= adjustedDayOfWeekFirst;
}
}
Upd: it appears to have at least twice better performance than #Atiris solution :)