C# Sort list, Logical Compare

Question

i have the following problem I have a list with strings for example (100_1, 100_2 .... , 100_10)

I sort the list with following code

extraImgsRaw.Sort((photo1, photo2) => photo1.CompareTo(photo2));

the result of this is : 100_1, 100_10, 100_2, 100_3 and so on

the result that I want is a logical compare like 100_1, 100_2 and then 100_10 so I prefer a Natural numeric sort not a Alphabetic sort. Do I need to write my own compare class that implements the ICompare interface or there is a build method in LINQ that does that?

thank you in advance

there's nothing built in. you can hack your own thing, or have a look at this: stackoverflow.com/questions/248603/natural-sort-order-in-c — David Hedlund
– David Hedlund, Commented Jul 1, 2010 at 12:13

LukeH · Accepted Answer · 2010-07-01 12:22:10Z

There's nothing built-in, but if the data is exactly as shown in your question then it shouldn't be too difficult to knock up a Comparison<T> to do this for you:

extraImgsRaw.Sort((x, y) => { // error checking etc removed for brevity int[] xi = x.Split('_').Select(int.Parse).ToArray(); int[] yi = y.Split('_').Select(int.Parse).ToArray(); int c = xi[0].CompareTo(yi[0]); return (c != 0) ? c : xi[1].CompareTo(yi[1]); });

A class or type would be better in this case IMO. You are likely to re-use it.
@leppie: If it's going to be re-used then I agree that an IComparer<T> with more error handling etc is the way to go. If it's just a quick one-off job where the user knows the exact format of the data then the Comparison<T> will usually suffice.
+1 for .Select(int.Parse) versus .Select(i => int.Parse(i))

leppie · Accepted Answer · 2010-07-01 12:18:18Z

Split and compare elements,

Here is one I wrote for 'versions'.

 /// <summary> /// Only works for version numbers in the form a ( . b ( . c ( . d )? )? )? /// </summary> public class VersionComponents : IComparable<VersionComponents> { readonly int[] components; int[] GetComponents(string cpnumber) { var tokens = cpnumber.Split(".".ToCharArray(), StringSplitOptions.RemoveEmptyEntries); return tokens.Select(x => Convert.ToInt32(x)).ToArray(); } public VersionComponents(string cpnumber) { components = GetComponents(cpnumber); } public int this[int index] { get { return components.Length > index ? components[index] : 0; } } public int CompareTo(VersionComponents other) { for (int i = 0; i < components.Length || i < other.components.Length; i++) { var diff = this[i].CompareTo(other[i]); if (diff != 0) { return diff; } } return 0; } }

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