Question

I want to sort already sorted list in this manner.

Already Sorted List =

Ali-23423423423
Ali-234234
Ali-234234255
Bali-36365356
Bali-32326546456
Bali-361111
Tali1-234234
Tali2-2342342
Tali3-23424

I am trying to find a query so that I can sort it like this

Ali-12315254
Bali-23346363
Tali-242452345
Ali-2342134134
Bali-234234234
Tali-242342

and So On.

I made a loop for the job but it is very slow and some what problematic as-well. Is there any solution?

while (List1.Count+10 < List.Count) 
{ 
    i++; 
    if (List.ElementAt(i).Remove(List.ElementAt(i).IndexOf('-')) == List1.ElementAt(i + 1).Remove(List1.ElementAt(i + 1).IndexOf('-'))) 
    { 
        String Element = List.ElementAt(i); 
        List.RemoveAt(i); 
        List.Add(Element); 
        i--; 
    } 
    else 
    { 
        List1.Add(List.ElementAt(i)); 
    } 
} 
List = List1; 

is the not so good way around I come up with

Answer 1

This query will give you unique items by name

var query = from s in list                        
            let name = s.Split('-')[0]
            group s by name into g
            orderby g.Key // don't sure if you need ordering
            select g.First();

UPDATE I think this code does exactly what you want – only first occurrence of every name is selected first, then second occurrences are selected, etc

List<string> sortedList = new List<string>();

while (list.Any())
{
    var query = list.GroupBy(s => s.Split('-')[0], (k,g) => g.First()).ToList();
    // list.RemoveAll(s => query.Contains(s));
    query.ForEach(s => list.Remove(s)); // I think this is more effective
    sortedList.AddRange(query);
}

Output for your sample data is:

Ali-23423423423 // first loop
Bali-36365356
Tali1-234234
Tali2-2342342
Tali3-23424
Ali-234234 // second loop
Bali-32326546456
Ali-234234255 // third loop
Bali-361111