Filter a Range of Dates with a String of Days

Question

I'm working with a collection of DateTime with all dates from Date A to Date B. I will be handed a string which looks like 1234567, 1 is sunday, 2 is tuesday, etc.

Now, imagine I want to filter my dates collection using a string with the above configuration and we get the string 1004007, meaning we will have to filter our DateTime collection to only have dates which occur on a sunday, on a wednesday and a saturday.

How can I read the whole string, figure out which days I will be filtering from and then dynamically filter my collection according to those days of the week?

Adam Robinson · Accepted Answer · 2011-01-17 17:58:14Z

2

Give this a shot:

List<DateTime> dates = ...;
string filter = "1004007";

List<DateTime> filteredDates = dates.Where(d =>
    filter.Contains(((int)d.DayOfWeek + 1).ToString())).ToList();

Or, if you like, you can first construct a list of days that are your filter rather than just using the String.Contains function. If your list of dates is very large, doing this work up front could help performance:

List<DateTime> dates = ...;
string filter = "1004007";
var daysOfWeek = filter.Distinct().Where(c => c != '0')
                       .Select(c => (DayOfWeek)(int.Parse(c.ToString()) - 1))

List<DateTime> filteredDates = (from d in dates
                                join dw in daysOfWeek on d.DayOfWeek equals dw
                                select d).ToList();

answered Jan 17, 2011 at 17:58

Adam Robinson

186k36 gold badges294 silver badges351 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Hallaghan Over a year ago

Thanks for your answer, it is quite complete and explains the solution well.

Mark Byers · Accepted Answer · 2011-01-17 17:55:28Z

1

Convert the day of the week to an integer, then a string, and use Contains to see if it is in your input string:

string days = "1004007";
var result = datetimes
   .Where(dt => days.Contains(((int)dt.DayOfWeek + 1).ToString()));

answered Jan 17, 2011 at 17:55

Mark Byers

844k202 gold badges1.6k silver badges1.5k bronze badges

4 Comments

Hallaghan Over a year ago

I'm sorry but I don't understand how I can loop through the string which says what days of the week we are filtering through to then filter the range of dates.

Mark Byers Over a year ago

@Hallaghan: You don't have to loop through the string. Contains does that for you.

Hallaghan Over a year ago

So it actually detects those numbers as being days inside the contains and filters the dates by them?

Mark Byers Over a year ago

@Hallaghan: It finds the day of the week for each date time, converts it to an integer between 1 and 7, then converts the integer to a string (a single character). It then tests to see if this character is contained in your input string using string.Contains.

Collectives™ on Stack Overflow

Filter a Range of Dates with a String of Days

2 Answers 2

1 Comment

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related