Question

We have some columns in a grid that contain numbers, strings, or strings that start with a number and the users expect them to sort in a sensible way. (The format depends on the customer so we don’t know the formats the strings will be in)

Is there a pre-canned” implementation of IComparable that does something like this?

Answer 1

here is a fast alphanumeric sort (can be used for other sorts with numerics too).

C# Alphanumeric Sorting http://www.dotnetperls.com/alphanumeric-sorting

var unordered = new[] { "100F", "50F", "SR100", "SR9" };
var ordered = unordered.OrderBy(s => s, new AlphanumComparatorFast());

and here is a nice article about the problem:

Sorting for Humans : Natural Sort Order http://www.codinghorror.com/blog/2007/12/sorting-for-humans-natural-sort-order.html

Here is the AlphanumComparatorFast class in case the above link stops working The end of the page states “It can be used in any program with no restrictions” and the comment at the start of the code also indicates it is free for use:

// NOTE: This code is free to use in any program.
// ... It was developed by Dot Net Perls.

public class AlphanumComparatorFast : IComparer
{
    public int Compare(object x, object y)
    {
        string s1 = x as string;
        if (s1 == null)
        {
            return 0;
        }
        string s2 = y as string;
        if (s2 == null)
        {
            return 0;
        }

        int len1 = s1.Length;
        int len2 = s2.Length;
        int marker1 = 0;
        int marker2 = 0;

        // Walk through two the strings with two markers.
        while (marker1 < len1 && marker2 < len2)
        {
            char ch1 = s1[marker1];
            char ch2 = s2[marker2];

            // Some buffers we can build up characters in for each chunk.
            char[] space1 = new char[len1];
            int loc1 = 0;
            char[] space2 = new char[len2];
            int loc2 = 0;

            // Walk through all following characters that are digits or
            // characters in BOTH strings starting at the appropriate marker.
            // Collect char arrays.
            do
            {
                space1[loc1++] = ch1;
                marker1++;

                if (marker1 < len1)
                {
                    ch1 = s1[marker1];
                }
                else
                {
                    break;
                }
            } while (char.IsDigit(ch1) == char.IsDigit(space1[0]));

            do
            {
                space2[loc2++] = ch2;
                marker2++;

                if (marker2 < len2)
                {
                    ch2 = s2[marker2];
                }
                else
                {
                    break;
                }
            } while (char.IsDigit(ch2) == char.IsDigit(space2[0]));

            // If we have collected numbers, compare them numerically.
            // Otherwise, if we have strings, compare them alphabetically.
            string str1 = new string(space1);
            string str2 = new string(space2);

            int result;

            if (char.IsDigit(space1[0]) && char.IsDigit(space2[0]))
            {
                int thisNumericChunk = int.Parse(str1);
                int thatNumericChunk = int.Parse(str2);
                result = thisNumericChunk.CompareTo(thatNumericChunk);
            }
            else
            {
                result = str1.CompareTo(str2);
            }

            if (result != 0)
            {
                return result;
            }
        }
        return len1 - len2;
    }
}