LINQ looking to sort one list into another which contains an array

Question

Looking to convert a list of sessions:

public class Sessions
    {
        public int SessionId {get; set; }
        public string Date { get; set; }
        public string Time { get; set; }
    }

into a list of DateOut:

public class DateOut
    {
        public int SessionId { get; set; }
        public string Date { get; set; }
        public List<string> Times { get; set; }
    }

Looking a result of to show each date with their associated times..

New to LINQ and C# so any help on getting this result through LINQ or another more practical solution would be great

What error you have? Also please show the code you are trying to write — Sergey Berezovskiy, Jan 08 '21 at 00:18
FYI, you should probably be using a `DateTime` property instead of `string` to capture the `Date` and `Time` components. — Rufus L, Jan 08 '21 at 01:17

greenjaed · Answer 1 · 2021-01-08T01:34:54.267

1

I'm assuming you're after something like this:

List<DateOut> DateOutList = SessionList
    .GroupBy(s => new { s.SessionId, s.Date}, it => it.Time)
    .Select(s => new DateOut {
        SessionId = s.Key.SessionId,
        Date = s.Key.Date,
        Times = s.ToList()
    })
    .ToList();

This assumes your date string is just the date. If it includes time components, you could do something like this:

List<DateOut> DateOutList = SessionList
    .GroupBy(s => new { s.SessionId, Date = Convert.ToDateTime(s.Date).Date}, it => it.Time)
    .Select(s => new DateOut {
        SessionId = s.Key.SessionId,
        Date = s.Key.Date.ToString(),
        Times = s.ToList()
    })
    .ToList();

While this will work, if you're doing anything else with Date and Time, I would recommend converting them to DateTime fields.

edited Jan 08 '21 at 01:34

answered Jan 08 '21 at 00:30

greenjaed

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Small correction: `Times = s.Select(it => it.Time).ToList()` – alexm Jan 08 '21 at 00:36
Yes this looks spot on but I don't get the groupby part, it's showing an error for SessionId and Date on the second line as they don't exist in this context – Ciarán Conville Jan 08 '21 at 00:43
Okay, I edited my answer to be syntactically correct – greenjaed Jan 08 '21 at 00:46
Very close but with a list of 7 I am getting a result of a list of 7 with a date and a time in each. But what I am after is if there are two entries with the same date, these should be one result with the date string and the 2 times in a list – Ciarán Conville Jan 08 '21 at 00:57
It's the full time for now but I plan to truncate on the frontend, but for now the time part is just something like `"2021-01-13T00:00:00.000Z"` – Ciarán Conville Jan 08 '21 at 01:04
I added more to the answer. Knowing nothing about your data, that should get you the groupings you want. – greenjaed Jan 08 '21 at 01:39

LINQ looking to sort one list into another which contains an array

1 Answers1