List<string> complex sorting

Question

I have a List<string> of sizes, say XS, S, M, L, XL, XXL, UK 10, UK 12 etc

What I want is to force the order to be that of above, regardless of the order of items in the list, I think I need a IComparable operator but unsure.

Ideally I want to have another List with the correct order in which it can reference it's 'place' in the list and re-sort itself, if it doesn't exist it will default to A-Z

Answer 1

You could also do something like this:

public class ShirtComparer : IComparer<string>
{
    private static readonly string[] Order = new[] { "XS", "S", "M", "L", "XL", "XXL", "UK10", "UK12" };

    public int Compare(string x, string y)
    {
        var xIndex = Array.IndexOf(Order, x);
        var yIndex = Array.IndexOf(Order, y);

        if (xIndex == -1 || yIndex == -1) 
            return string.Compare(x, y, StringComparison.Ordinal);

        return xIndex - yIndex;
    }
}

Usage:

var list = new List<string> { "S", "L", "XL", "L", "L", "XS", "XL", "XXXL", "XMLS", "XXL", "AM19" };
var result = list.OrderBy(size => size, new ShirtComparer());

It should also default to A-Z for values not in the list...

Answer 2

Create an array of sizes in the order you want them to be in, then sort the shirts by the position of their sizes in that array:

string[] sizes = new [] {"XS", "S", "M", "L", "XL", "XXL", "UK 10", "UK 12"};

var shirtsInOrder = shirts
                        .OrderBy(s=>sizes.Contains(s) ? "0" : "1")  // put unmatched sizes at the end
                        .ThenBy(s=>Array.IndexOf(sizes,s))  // sort matches by size
                        .ThenBy(s=>s); // sort rest A-Z

Answer 3

var order = new string[] { "XS", "S", "M", "L", "XL", "XXL", "UK10", "UK12" };

var orderDict = order.Select((c, i) => new { sze = c, ord = i })
            .ToDictionary(o => o.sze, o => o.ord);

var list = new List<string> { "S", "L", "XL", "L", "L", "XS", "XL" };
var result = list.OrderBy(item => orderDict[item]);

Answer 4

You can use OrderByDescending + ThenByDescending directly:

sizes.OrderByDescending(s => s == "XS")
     .ThenByDescending( s => s == "S")
     .ThenByDescending( s => s == "M")
     .ThenByDescending( s => s == "L")
     .ThenByDescending( s => s == "XL")
     .ThenByDescending( s => s == "XXL")
     .ThenByDescending( s => s == "UK 10")
     .ThenByDescending( s => s == "UK 12")
     .ThenBy(s => s);

I use ...Descending since a true is similar to 1 whereas a false is 0.