How to sort out numeric strings as numerics?

Question

If you have strings like:

\"file_0\"
\"file_1\"
\"file_2\"
\"file_3\"
\"file_4\"
\"file_5\"
\"file_6\"
\"file_11\"

how can you sort them so

Answer 1

I have used the following approach in a project a while ago. It's not particularly efficient, but if the number of items to sort is not huge it performed well enough for that use. What it does is that it splits up the strings to compare into arrays on the '_' character, and then compares each element of the arrays. An attempt is made to parse the last element as an int, and make a numeric comparison there.

It also has an early exit if the input strings would contain a different number of elements (so if you compare "file_nbr_1" to "file_23", it will not go into comparing each part of the strings, but rather just to a regular string comparison on the full strings):

char[] splitChars = new char[] { '_' };
string[] strings = new[] {
    "file_1",
    "file_8",
    "file_11",
    "file_2"
};

Array.Sort(strings, delegate(string x, string y)
{
    // split the strings into arrays on each '_' character
    string[] xValues = x.Split(splitChars);
    string[] yValues = y.Split(splitChars);

    // if the arrays are of different lengths, just 
    //make a regular string comparison on the full values
    if (xValues.Length != yValues.Length)
    {
        return x.CompareTo(y);
    }

    // So, the arrays are of equal length, compare each element
    for (int i = 0; i < xValues.Length; i++)
    {
        if (i == xValues.Length - 1)
        {
            // we are looking at the last element of the arrays

            // first, try to parse the values as ints
            int xInt = 0;
            int yInt = 0;
            if (int.TryParse(xValues[i], out xInt) 
                && int.TryParse(yValues[i], out yInt))
            {
                // if parsing the values as ints was successful 
                // for both values, make a numeric comparison 
                // and return the result
                return xInt.CompareTo(yInt);
            }
        }

        if (string.Compare(xValues[i], yValues[i], 
            StringComparison.InvariantCultureIgnoreCase) != 0)
        {
            break;
        }
    }

    return x.CompareTo(y);

});