NaturalComparer to compare string with numerics

NaturalComparer.cs

//
// Based on https://stackoverflow.com/a/5641272/199551
//
public class NaturalComparer : IComparer<string>
{
	public static readonly NaturalComparer Instance = new NaturalComparer();
  
	private NaturalComparer() { }
  
	public int Compare(string x, string y)
	{
		if (x == null && y == null) return 0;
		if (x == null) return -1;
		if (y == null) return 1;

		int lx = x.Length, ly = y.Length;

		for (int mx = 0, my = 0; mx < lx && my < ly; mx++, my++)
		{
			if (char.IsDigit(x[mx]) && char.IsDigit(y[my]))
			{
				long vx = 0, vy = 0;

				for (; mx < lx && char.IsDigit(x[mx]); mx++)
					vx = vx * 10 + x[mx] - '0';

				for (; my < ly && char.IsDigit(y[my]); my++)
					vy = vy * 10 + y[my] - '0';

				if (vx != vy)
					return vx > vy ? 1 : -1;
			}

			if (mx < lx && my < ly && x[mx] != y[my])
				return x[mx] > y[my] ? 1 : -1;
		}

		return lx - ly;
	}
}