Question

I have a list of strings that can contain a letter or a string representation of an int (max 2 digits).
They need to be sorted either alphabetically or (when it is actually an int) on the numerical value it represents.

Example:

IList<string> input = new List<string>()
    {"a", 1.ToString(), 2.ToString(), "b", 10.ToString()};

input.OrderBy(s=>s)
  // 1
  // 10
  // 2
  // a
  // b

What I would want is

  // 1
  // 2
  // 10
  // a
  // b

I have some idea involving formatting it with trying to parse it, then if it is a successfull tryparse to format it with my own custom stringformatter to make it have preceding zeros. I’m hoping for something more simple and performant.

Edit
I ended up making an IComparer I dumped in my Utils library for later use.
While I was at it I threw doubles in the mix too.

public class MixedNumbersAndStringsComparer : IComparer<string> {
    public int Compare(string x, string y) {
        double xVal, yVal;

        if(double.TryParse(x, out xVal) && double.TryParse(y, out yVal))
            return xVal.CompareTo(yVal);
        else 
            return string.Compare(x, y);
    }
}

//Tested on int vs int, double vs double, int vs double, string vs int, string vs doubl, string vs string.
//Not gonna put those here
[TestMethod]
public void RealWorldTest()
{
    List<string> input = new List<string>() { "a", "1", "2,0", "b", "10" };
    List<string> expected = new List<string>() { "1", "2,0", "10", "a", "b" };
    input.Sort(new MixedNumbersAndStringsComparer());
    CollectionAssert.AreEquivalent(expected, input);
}

Answer 1

Perhaps you could go with a more generic approach and use a natural sorting algorithm such as the C# implementation here.