How can i sort List<string> by digits lowest to highest when the digits are part of the strings?

Question

I have this sort method:

public List<string> SortList(List<string> thread)
        {
            thread = thread
    .OrderBy(str =>
    {
        var match = Regex.Match(str, @"^([-+]?\d+)");
        return match.Success ? int.Parse(match.Groups[1].Value) : int.MaxValue;
    })
    .ToList();
            responsers.Add(new List<string>(thread));
            return thread;
        }

And this is the method that call this SortList:

public List<string> GetResponsers(string contents)
        {
            string responser = "";
            List<string> threadList = new List<string>();
            int f = 0;
            int startPos = 0;
            while (true)
            {
                string firstTag = "<FONT CLASS='text16b'>";
                string lastTag = "&n";
                f = contents.IndexOf(firstTag, startPos);
                if (f == -1)
                {
                    break;
                }
                int g = contents.IndexOf(lastTag, f);
                startPos = g + lastTag.Length;
                responser = contents.Substring(f + 22, g - f - 22);
                threadList.Add(responser);
            }
            SortList(threadList);
            return threadList;
        }

The method GetResponsers get content of html file. And i'm parsing some stuff from it. In the end i have a List called: threadList

This method is calling each time with another content and parse stuff from it. For example in the end in this case threadList contain 9 items. The first item in index 0 is the title so it dosent have a number so i don't want to touch it to leave it in index 0 for exampe:

Hello world ?? (*)

Now in index 1 i have also text but with a number before it: "1. this is new" In index 2 i have also text with a number: "4. hello" And so on untill the lasti nde: "2. last item"

The problem is that in index 1 i can have "3. fgfgfg" In index 3 "6. fgfdghjj"

And i want to sort the List by the digits but the digits are part of each string !

In index 1 for example i have "3. hello world" The number 3 is not int. The number 3 is string.

I used a breakpoint and the SortList is not working good it's not sorting the List each time by the digits. In the end i want the List threadList to be only strings but the digits to be from first digit to last:

"this is the title"
"1. hello"
"2. hello world"
"3. this is third item"
"4. fourth item digits are strings"
"5. this is a test"
"6. this is after sorted"
"7. this is the last item"

The parsing method GetResponsers is working as i wanted the problem is how to sort the List by the digits when the digits are part of the strings in each index.

Answer 1

This code would work for positive single digits at the beginning:

public List<string> SortList(List<string> thread)
{
    var first = thread.Take(1);
    var ordered = thread.Skip(1).OrderBy(s=>char.GetNumericValue(s[0]));
    thread = first.Concat(ordered).ToList();
    return thread;
}

You should consider making this method returning just void btw. So either this

public void SortList(List<string> thread)
{
    var first = thread.Take(1);
    var ordered = thread.Skip(1).OrderBy(s=>char.GetNumericValue(s[0]));
    thread = first.Concat(ordered).ToList();
}

or my favourite

public List<string> SortList(List<string> thread)
{
    var first = thread.Take(1);
    var ordered = thread.Skip(1).OrderBy(s=>char.GetNumericValue(s[0]));
    return first.Concat(ordered).ToList();
}

although the last one needs you to change the calling code to return SortList(threadList);

Answer 2

Try this:

List<string> list; // this is your input list

var firstRow = list.Take(1);
var orderedRows = list.Skip(1)
    .OrderBy(s=>Int32.Parse(s.Split(' ')[0].TrimEnd('.')));
var result = firstRow.Concat(orderedRows).ToList();

If you like shorter, but less readable code:

var result = list.Take(1)
    .Concat(list.Skip(1)
    .OrderBy(s => Int32.Parse(s.Split(' ')[0].TrimEnd('.')))).ToList();

This way you are not limited to strings with one-digit number at the start.

All your input strings have to start with a number followed by a dot and a space, like so:

"1. "

Example input:

"this is the title"
"6. this is after sorted"
"1. hello"
"2. hello world"
"82. fourth item digits are strings"
"3. this is third item"
"5. this is a test"
"731. this is the last item"

And output:

"this is the title"
"1. hello"
"2. hello world"
"3. this is third item"
"5. this is a test"
"6. this is after sorted"
"82. fourth item digits are strings"
"731. this is the last item"