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.OrderBy(x => DateTime.Parse(x[1]));

Answer 2

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);
    }
}

Answer 3

Maybe something like

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((a, b) =>
    {
        string[] aSplit = a.Split(',');
        string[] bSplit = b.Split(',');

        if (aSplit.Count() < 2 && bSplit.Count() < 2) 
            return a.CompareTo(b);

        DateTime date1, date2;

        if (!DateTime.TryParse(aSplit[1].Trim(), out date1) || 
            !DateTime.TryParse(bSplit[1].Trim(), out date2))
            return a.CompareTo(b);

        return date2.CompareTo(date1);
    });

Answer 4

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 5

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 6

If your String contains anything other then a date, then I highly recommend splitting your string into JUST the date part, then TryParse and compare that value. Not the whole string!

yourStringList.Sort(
    (x, y) => {
        DateTime ix;
        DateTime iy;
        DateTime.TryParse(x.Split('(')[2].Split(')')[0], out ix);
        DateTime.TryParse(y.Split('(')[2].Split(')')[0], out iy);
        return ix.CompareTo(iy);
    }
);

In this example, im splitting my string to exactly the part where the date lies , and using tryparse on that. Only after that is parsed correctly can your comparing be done properly.