Pruning List of Times During the Day to Remove Times in the Past

Question

In a C# / WPF application I have a list of type string that is the ItemsSource of a combobox. This list contains half-hour chunks of time that are free on the user's calendar for the current day (from 8am to 5pm). Pictured here:

enter image description here

I would like to trim the list so that times in the past are not shown (e.g. If it's presently 10am, don't show chunks of time from 8am-10am). How can I best accomplish this?

Update: The list of strings is composed of "startTime" + " - " + "endTime", so each entry in the list looks like:

6/10/2014 8:00:00 AM - 6/10/2014 8:30:00 AM
6/10/2014 8:30:00 AM - 6/10/2014 9:00:00 AM
etc...

There are several different ways depending on your implementation. Have you tried anything at all yet? — Andrew, Jun 10 '14 at 15:33
Can you give us a sample of what your `List` for times looks like? — Elias, Jun 10 '14 at 15:34
I have updated my question to include more details about the list. — user3342256, Jun 10 '14 at 15:44
possible duplicate of [Filtering collections in C#](http://stackoverflow.com/questions/26196/filtering-collections-in-c-sharp) — Sean Airey, Jun 10 '14 at 15:49

score 2 · Accepted Answer · answered Jun 10 '14 at 16:03

2

I figured it out by using a bit of lambda expressions. Say your list of times is called:

times

then using the where clause, we can then get all the times after now by using:

List<string> ordered = times.Where(o => DateTime.Parse(o.Split('-')[1]) > DateTime.Now).ToList();

This basically parses each element in your 'times' list into a DateTIme type and then sees if it is after the current DateTime.

answered Jun 10 '14 at 16:03

Elias

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That's really slick and is almost perfect, however because it's evaluating both DateTime objects on either side of "-" it's still returning some unusable times. For instance if it's 9:15am, you'd still see an item indicating you're available from 9:00 - 9:30 because 9:30 isn't in the past. To fix this, you'd just need to evaluate times on the left of the hyphen character. How could your expression be re-written to do that? – user3342256 Jun 10 '14 at 16:10
You would change `o.Split('-')[1]` to `o.Split('-')[0]` to evaluate the left hand time – Elias Jun 10 '14 at 16:12

score 1 · Answer 2 · answered Jun 10 '14 at 16:06

Using LinQ is usually the easiest way to filter a collection. Clearly however, this is going to be far more difficult if you stick with string values, so I'm going to look at this from a different angle - just recreating the collection each two hours. In this case, the filtering would be unnecessary... try something like this:

List<DateTime> validDates = new List<DateTime>();
DateTime startTime = DateTime.Now.Date;
for (int index = 0; index < 48; index++)
{
    if (startTime > DateTime.Now)
    {
        validDates.Add(startTime);
    }
    startTime = startTime.AddMinutes(30);
}

I'll leave it up to you how you want to populate your string values from these valid DateTime instances.

Pruning List of Times During the Day to Remove Times in the Past

2 Answers2