I am trying to get Date of a specific day based on its sequence in a week like
GetDate(22, 4);
which needs to return the date of 4th day in 22nd weeks of current year. How can I do this?
void Main()
{
int months;
var year = DateTime.Now.ToString("yyyy");
months = GetWeeksInYear( Convert.ToInt32(year));
Console.WriteLine(months);
}
public int GetWeeksInYear(int year)
{
DateTimeFormatInfo dfi = DateTimeFormatInfo.CurrentInfo;
DateTime date1 = new DateTime(year, 12, 31);
Calendar cal = dfi.Calendar;
return cal.GetWeekOfYear(date1, dfi.CalendarWeekRule, dfi.FirstDayOfWeek);
}
public int GetDate(int weekNo, int dayNo)
{
return // Date
}
You can just add the number of days from the beginning of the year:
var dt = new DateTime(year, 1, 1);
dt = dt.AddDays(weekNo * 7 + dayNo);
var date = dt.Date;
I think a simple way would be to take Jan 1 of year and add number of days,
DateTime day = new DateTime(year, 1, 1).AddDays((week * 7) + days);
firstable the week of the year is a calendar calculation and locale dependent value so you have to consider that when giving the week number...
So you are for sure missing the use of something like
CultureInfo.CurrentCulture.Calendar;
Related
My goal is to figure out the difference between two dates and then add that amount of days to the original start.
DateTime originalStart = new DateTime(2015, 1, 1);
DateTime newDate = originalStart.AddDays((endDate - startDate).TotalDays);
For example with the following params:
original start: 1/1/2015
start date: 1/1/2016
end date: 1/1/2017
newDate should be: 1/1/2016 (difference between start and end is 1 year so then we add that one year to original start)
My problem is that if a leap year is part of the date difference between endDate and startDate and then I go and add those days to originalStart. I end up with dates like 1/2/2016 for newDate.
Any idea how I can avoid leap years here to make sure if the difference between 1/1/2016 and 1/1/2017 is rounded. I would only like to add exactly one year to originalStart and not the extra day because of the leap year.
DateTime originalStart = new DateTime(2015, 1, 1);
DateTime zeroTime = new DateTime(1, 1, 1);
DateTime endDate = new DateTime(2016, 1,1);
endDate .Dump();
DateTime startDate= new DateTime(2017, 1,1);
startDate.Dump();
TimeSpan span = startDate- endDate ;
// because we start at year 1 for the Gregorian
// calendar, we must subtract a year here.
int years = (zeroTime + span).Year - 1;
int months = (zeroTime + span).Month - 1;
int days = (zeroTime + span).Day;
years.Dump();
months.Dump();
days.Dump();
originalStart= originalStart.AddMonths(months);
originalStart = originalStart.AddYears(years);
originalStart = originalStart.AddDays(days);
My task is to find all Friday, 13 in a year that user inputs.
Can somebody explain how to do it? (I'm a beginner in c#)
int year = 2015;
for(int m=1; m<=12; m++)
{
var dt = new DateTime(year, m, 13);
if (dt.DayOfWeek == DayOfWeek.Friday)
Console.WriteLine(dt.ToShortDateString());
}
To obtain the dates you may use Linq:
var dates = Enumerable
.Range(1, 12) // All months
.Select(month => new DateTime(2015, month, 13))
.Where(date => date.DayOfWeek == DayOfWeek.Friday);
To print out them
Console.WriteLine(String.Join(Environment.NewLine, dates));
If you want to get these dates in Gregorian Calender, you can use a combination of a loop, DateTime constructor and DayOfWeek enumeration like;
int year = 2015;
for (int i = 1; i < 13; i++)
{
if(new DateTime(year, i, 13).DayOfWeek == DayOfWeek.Friday)
Console.WriteLine(new DateTime(year, i, 13));
}
For 2015, result will be;
13.02.2015 00:00:00
13.03.2015 00:00:00
13.11.2015 00:00:00
If you want to number of months, you can use .Month property of the result like;
Console.WriteLine((new DateTime(year, i, 13)).Month);
If you want to get your month names based on your CurrentCulture, you can use custom MMMM specifier like;
Console.WriteLine((new DateTime(year, i, 13)).ToString("MMMM"));
Also you can use Enumerable.Range like;
List<int> monthList = Enumerable.Range(1, 12).
Where(d => new DateTime(2015, d, 13).DayOfWeek == DayOfWeek.Friday).
ToList(); // {2, 3, 11}
or
List<string> monthList = Enumerable.Range(1, 12).
Where(d => new DateTime(2015, d, 13).DayOfWeek == DayOfWeek.Friday).
Select(m => new DateTime(2015, m, 13).ToString("MMMM", CultureInfo.InvariantCulture)).
ToList(); // {February, March, November}
Try to inspire by the code showed in that thread:
Finding every friday from start date till the end of the year
(of course you will have to check if selected Friday is 13th)
It can be done like this using linq.
var year = 2015;
var months = new[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 };
var unluckyDays = months.Select(m => new DateTime(year, m, 13)).Where(dt => dt.DayOfWeek == DayOfWeek.Friday);
The first Select statement projects the list of integers into a list of datetimes representing the 13th of each month in the year specified.
Then simply filter this list to those where the day of the week is Friday.
DateTime objects have a property on them called DayOfWeek. You can utilize this to help you figure out if a date supplied returns a DayOfWeek Value of Friday: see below:
static void Main(string[] args)
{
for (var i = 1; i < 12; i++)
{
DateTime date = new DateTime(2015, i, 13);
if (date.DayOfWeek == DayOfWeek.Friday)
Console.WriteLine(date.ToShortDateString());
}
Console.ReadLine();
}
Yes, it is quite simple
int year = 2014;
DateTime day = new DateTime(2014,1,1);
while (day.Year == year)
{
if (day.DayOfWeek == DayOfWeek.Friday && day.Day == 13)
{
Console.WriteLine(day);
}
day = day.AddDays(1);
}
You init a DateTime variable in the start of the year
Then you loop over each day of the year in this code I printed it
You can find more info of the DateTime class here
DateTime Day of the week
DateTime referenc in MSDN
I have a function that get the current weeknumber from the given date
e.g.
GregorianCalendar cal = new GregorianCalendar(GregorianCalendarTypes.Localized);
return cal.GetWeekOfYear(date, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);
gives back weeknumber 40 for DateTime.Now.
So my question is , also my problem, i need to get the dates in the returned week. I've tried several thing and none so for worked.
You can use the class Week of the Time Period Library for .NET:
Week week = new Week( new DateTime( 2012, 03, 21 ) );
Console.WriteLine( "week #: ", week.WeekOfYear );
Console.WriteLine( "week first day: ", week.FirstDayOfWeek );
Console.WriteLine( "week last day: ", week.LastDayOfWeek );
Additional, the class Week supports ISO 8601 week numbering and custom cultures.
You could use this function to get the first date of a week:
public static DateTime FirstDateOfWeek(int year, int weekOfYear)
{
DateTime jan1 = new DateTime(year, 1, 1);
int daysOffset = Convert.ToInt32(System.Globalization.CultureInfo.CurrentCulture.DateTimeFormat.FirstDayOfWeek) - Convert.ToInt32(jan1.DayOfWeek);
DateTime firstWeekDay = jan1.AddDays(daysOffset);
System.Globalization.CultureInfo curCulture = System.Globalization.CultureInfo.CurrentCulture;
int firstWeek = curCulture.Calendar.GetWeekOfYear(jan1, curCulture.DateTimeFormat.CalendarWeekRule, curCulture.DateTimeFormat.FirstDayOfWeek);
if (firstWeek <= 1) {
weekOfYear -= 1;
}
return firstWeekDay.AddDays(weekOfYear * 7);
}
Then you can get all dates in this week in the following way:
var firstDate = FirstDateOfWeek(2012, 40);
var allWeekDays = new List<DateTime>();
allWeekDays.Add(firstDate);
var currentDate = firstDate;
for(int d = 1; d < 7; d++)
{
currentDate=currentDate.AddDays(1);
allWeekDays.Add(currentDate);
}
or in one line:
var week = Enumerable.Range(0,7).Select(d => firstDate.AddDays(d)).ToList();
You can get the first and last day in the week simply by looking at the weekday of the given date, and look for the monday:
DateTime firstDay = date.Date;
while (firstDay.DayOfWeek != DayOfWeek.Monday) {
firstDay = date.AddDays(-1);
}
DateTime lastDay = firstDay.AddDays(6);
i want to pass in a year and get a date back that represents the first monday of the first week
so:
If a passed in 2011, i would get back Jan 3, 2011
If a passed in 2010, i would get back Jan 4, 2010
private DateTime GetFirstMondayOfYear(int year)
{
DateTime dt = new DateTime(year, 1, 1);
while (dt.DayOfWeek != DayOfWeek.Monday)
{
dt = dt.AddDays(1);
}
return dt;
}
Try this for a solution without looping:
public DateTime FirstMonday(int year)
{
DateTime firstDay = new DateTime(year, 1, 1);
return new DateTime(year, 1, (8 - (int)firstDay.DayOfWeek) % 7 + 1);
}
You can use GetFirstMonday(2010) for getting first Monday for Jan 2010. Or you can specify month also with GetFirstMonday(2010, 2) to get first Monday for Feb 2010.
GetFirstDayOfMonth can get any first day for given month, need to pass DayOfWeek value for to get result of required day.
// Common function to get first day for any month & year.
public DateTime GetFirstDayOfMonth(int year, int month, int day)
{
return new DateTime(year, month, 1)
.AddDays((7 - datetime.DayOfWeek.GetHashCode() + day) % 7);
}
public DateTime GetFirstMonday(int year, int month = 1)
{
return GetFirstDayOfMonth(year, month, DayOfWeek.Monday.GetHashCode());
}
I am stuck for sometime now, now need your help.
I want to display in a dropdown only fourth Sunday of each month, say from 1-Sep-2010 to 31-Aug-2011
I only want fourth Sunday in dropdown list, how to do it using asp.net C#
Regards
Here is an approach that uses a little LINQ and the knowledge that the fourth Sunday will occur between the 22nd and 28th of a month, inclusive.
DateTime startDate = new DateTime(2010, 9, 1);
DateTime endDate = startDate.AddYears(1).AddDays(-1);
List<DateTime> fourthSundays = new List<DateTime>();
DateTime currentDate = startDate;
while (currentDate < endDate)
{
// we know the fourth sunday will be the 22-28
DateTime fourthSunday = Enumerable.Range(22, 7).Select(day => new DateTime(currentDate.Year, currentDate.Month, day)).Single(date => date.DayOfWeek == DayOfWeek.Sunday);
fourthSundays.Add(fourthSunday);
currentDate = currentDate.AddMonths(1);
}
You can then bind that List<DateTime> to the dropdown or skip the list itself in favor of adding the items as you generate them to the dropdown, like below.
yourDropdown.Items.Add(new ListItem(fourthSunday.ToString()));
For giggles, you can do the whole thing in a LINQ statement and skip (most of) the variables.
DateTime startDate = new DateTime(2010, 9, 1);
IEnumerable<DateTime> fourthSundays =
Enumerable.Range(0, 12)
.Select(item => startDate.AddMonths(item))
.Select(currentMonth =>
Enumerable.Range(22, 7)
.Select(day => new DateTime(currentMonth.Year, currentMonth.Month, day))
.Single(date => date.DayOfWeek == DayOfWeek.Sunday)
);
Got bored so here you go. Two helper methods one retrieves the Week if it exist, and the other iterates through the months
class Program
{
static void Main(string[] args)
{
DateTime startDate = new DateTime(2010, 09, 1);
foreach(DateTime dt in EachMonth( new DateTime(2010, 09, 1), new DateTime(2011, 09, 1))){
DateTime? result = GetDayByWeekOffset(DayOfWeek.Sunday, dt, 4);
Console.WriteLine("Sunday:" + (result.HasValue?result.Value.ToString("MM-dd-yyyy"):"null"));
}
Console.ReadKey();
}
public static DateTime? GetDayByWeekOffset(DayOfWeek day, DateTime month, int weekOffSet)
{
//First day of month
DateTime firstDayOfMonth = month.AddDays((-1 * month.Day) + 1);
//
int daysOffSet;
daysOffSet= ((int)day + 7 - (int)firstDayOfMonth.DayOfWeek) % 7;
DateTime firstDay = month.AddDays(daysOffSet);
// Add the number of weeks specified
DateTime resultDate = firstDay.AddDays((weekOffSet - 1) * 7);
if (resultDate.Month != firstDayOfMonth.Month){
return null;
}else{
return resultDate;
}
}
public static IEnumerable<DateTime> EachMonth(DateTime from, DateTime thru)
{
for (var month = from.Date; month.Date <= thru.Date; month = month.AddMonths(1))
yield return month;
}
}
Anthony's answer above is nice, I like it a lot. As an alternate, here is a method which is parameterized for the day of the week and the week number (i.e. if you need other combinations, like 4th Sunday, 3rd Friday, etc.) with some comments.
Call it like this for your case:
List<DateTime> sundays = DateInstances(new DateTime(2010, 9, 1), new DateTime(2011, 8, 31), DayOfWeek.Sunday, 4);
And the method itself:
public List<DateTime> DateInstances(DateTime start, DateTime end, DayOfWeek day, int weeks)
{
if (start > end)
throw new ArgumentOutOfRangeException("end", "The start date must occur before the end date");
List<DateTime> results = new List<DateTime>();
DateTime temp = start;
while (temp < end)
{
DateTime firstWeekday = new DateTime(temp.Year, temp.Month, 1);
//increment to the given day (i.e. if we want the 4th sunday, we must find the first sunday of the month)
while (firstWeekday.DayOfWeek != day)
firstWeekday = firstWeekday.AddDays(1);
//add the number of weeks (note: we already have the first instance, so subtract 1)
firstWeekday = firstWeekday.AddDays(7 * (weeks - 1));
//make sure we haven't gone over to the next month
if (firstWeekday.Month == temp.Month)
results.Add(firstWeekday);
//let's not loop forever ;)
temp = temp.AddMonths(1);
}
return results;
}