Question

I have an extension class that is converting an Observable collection to list and performing an order by. This logic is working but I need it to sort Alpha-numeric as well. E.g.

In lieu of A1 A10 A2 A3 should be A1 A2 A3 A10.

What is the best way to go about this?

<pre>

public static void Sort<T>(this ObservableCollection<T> collection, Comparison<T> comparison)
    {
        var comparer = new Comparer<T>(comparison);

        List<T> sorted = collection.OrderBy(x => x, comparer).ToList();

        for (int i = 0; i < sorted.Count(); i++)
            collection.Move(collection.IndexOf(sorted[i]), i);
    }


    internal class Comparer<T> : IComparer<T>
{
    private readonly Comparison<T> comparison;

    public Comparer(Comparison<T> comparison)
    {
        this.comparison = comparison;
    }
    #region IComparer<T> Members

    public int Compare(T x, T y)
    {   
        return comparison.Invoke(x, y);
    }
}

</pre>

Answer 1

Parse the string into two parts, the alpha part and the number part. Put the number part into an int, and then compare the int part only when the alpha part is a tie.

public int Compare(string left, string right) {
  string leftAlpha;
  int leftNum;
  string rightAlpha;
  int rightNum;

  GetParts(left, out leftAlpha, out leftNum);
  GetParts(right, out rightAlpha, out rightNum);

  if (leftAlpha != rightAlpha) {
     return String.Compare(leftAlpha, rightAlpha);
  }
  else {
     return leftNum.CompareTo(rightNum);
  }
}

private void GetParts(string str, out string alpha, out string num) {
  alpha = str.Substring(0, 1);
  string numStr = str.Substring(1);
  num = Int32.Parse(numStr);
}

---

If you can find a way to expose those two parts as properties on a class, you might be best off using a CollectionView to bind to. Where the SourceCollection is your ObservableCollection, and then add SortDescriptions which correspond to the properties on the class. That could be overkill, but does have a lot of benefits like inserting new elements directly into the right position. You won’t have to do any sorting on the collections explicitly at all.