How do I sort a custom array list by the dateTime elements

Question

I have an ArrayList with instances of a class (in this case 'loan'). This loan class contains a variable 'date'. I want to sort my ArrayList by these date variables in the most optimum way.

The way I have done date sorting before, is to use a List<DateTime>. but in this case I want to sort a list/arraylist, keeping the rest of the information, so all the information can be used elsewhere

Note: If you mix local and UTC dates it will sort by the raw time, and not do timezone conversion. — CodesInChaos, Dec 01 '10 at 15:40

Steven · Answer 1 · 2010-12-01T15:43:31.657

3

You can use the System.Linq.Enumerable extension methods Cast<T> and OrderBy for this:

ArrayList list;

List<Loan> loanes = (
    from loan in list.Cast<Loan>()
    orderby loan.Date
    select loan).ToList();

edited Dec 01 '10 at 15:43

answered Dec 01 '10 at 15:38

Steven

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Calling the result `sortedList` is misleading because it's an (ordered) enumerable and not a list. – CodesInChaos Dec 01 '10 at 15:41

score 2 · Answer 2 · answered Dec 01 '10 at 15:38

2

You need to make an IComparer<Loan> that returns x.Date.CompareTo(y.Date).

answered Dec 01 '10 at 15:38

SLaks

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score 1 · Accepted Answer · answered Dec 01 '10 at 15:48

What Slaks said basically to sort in place in the ArrayList you need a custom IComparer implementation, I put a sample below:

public class Loan
{
    public DateTime date { get; set; }

}

public class LoanComparer : IComparer
{
    public int Compare(object x, object y)
    {
        Loan loanX = x as Loan;
        Loan loanY = y as Loan;

        return loanX.date.CompareTo(loanY.date);
    }
}


static void Main(string[] args)
{
    Loan l1 = new Loan() {date = DateTime.Now};
    Loan l2 = new Loan() { date = DateTime.Now.AddDays(-5) };

    ArrayList loans = new ArrayList();
    loans.Add(l1);
    loans.Add(l2);


    loans.Sort(new LoanComparer());
}

How do I sort a custom array list by the dateTime elements

3 Answers3