List of Lists Sort With String Dates?

Question

I have a list of string lists that contains DateTime values converted to strings. There are other values in the list, so I can't make the list a full DateTime list.

I have a line of code that sorts the list, but it sorts the dates by their string value, not DateTime value (which is what I want). How can I modify my code to correctly sort by the DateTime?

//This sorts the parent list by the 2nd column of the child list
List.Sort((a, b) => -1 * a[1].CompareTo(b[1]));

edit:

Sample List Contents:
Value1, 2010-06-28 10:30:00.000
Value2, 2010-06-27 10:30:00.000
Value2, 2010-06-26 10:30:00.000

Answer 1

Try the folloting

List.Sort((a,b) => -1 * DateTime.Parse(a[1]).CompareTo(DateTime.Parse(b[1])));

Or if you have LINQ handy and don't need an inplace sort

var sorted = myList.Sort(x => DateTime.Parse(x[1]));

Answer 2

You first parse the string into a DateTime. Assuming the second columns is always a well-formed date/time string. The code below uses Linq to create a separate sorted list:

sortedList = yourList.OrderBy( item => DateTime.Parse( item[1] ) ).ToList();

If you need to sort in place, you can do so using:

List.Sort((a,b)=>return DateTime.Parse(b[1]).CompareTo(DateTime.Parse(a[1]) );

Depending on how your dates are repsented, you may want to consider using DateTime.ParseExact().

Answer 3

You need to convert a[1] to date time before comparing it.

List.Sort((a, b) => -1 * DateTime.Parse(a[1]).CompareTo(DateTime.Parse(b[1])))

EDIT:

If your LINQ query that fills the list is filling it as a list of strings, then you need to get a substring of the item that represents the date portion of the string. DateTime.Parse won't just magically pick out the part of the string that has a date value in it.

If this is the case and you're considering using string.Split, be sure you know the format your date will be coming, since some formats allow commas.

Answer 4

You should create your own custom comparer.

class Program
{
    static void Main(string[] args)
    {
        List<string> list = new List<string>
                                {
                                    "Value1, 2010-06-28 10:30:00.000",
                                    "Value2, 2010-06-27 10:30:00.000",
                                    "Value3, 2010-06-26 10:30:00.000"
                                };

        list.Sort(new MyComparer());
    }
}

internal class MyComparer : IComparer<string>
{
    public int Compare(string x, string y)
    {
        var xItems = x.Split(new []{','});
        var yItems = y.Split(new []{','});
        var xDateTime = DateTime.Parse(xItems[1]);
        var yDateTime = DateTime.Parse(yItems[1]);
        return xDateTime.CompareTo(yDateTime);
    }
}