Arraylist in arraylist sorting

Question

I have an arraylist. it keeps arraylists in it. For example;

 ar1 -> {2,3,46,67}  keeps 4 members. 
 ar2 -> {28,96,67} keeps 3 members.
 ar2 -> {56,32,67,54,214} keeps 5 members. 
 Ar_main[0]= ar1 
 Ar_main[1]= ar2 
 Ar_main[2]= ar3

i want to sort ar_main order by count of members. i used bubble sort algorithm. but it didn't work, can't we sort arraylist like this method?

private void sortArrayToAscending(ArrayList ar)
    {
        ArrayList ar1,ar2;
        for (int i = 0; i < ar.Count - 1; i++) 
         for (int j = 1; j < ar.Count - i; j++)
          {
             ar1 = (ArrayList)ar[j];
             ar2 = (ArrayList)ar[j-1];
             if (ar1.Count < ar2.Count)
             {
                 ArrayList temp = ar2;
                 ar2=ar1;
                 ar1=temp;             
             }           
          }
    }

Answer 1

There is a built-in Sort method in the ArrayList that does the sorting for you. What you have to provide is an IComparer implementation that compares the list, making their length the criteria:

public void ArrayListSort()
{
    var list = new ArrayList();
    list.Sort(new LengthComparer());
}

class LengthComparer : IComparer
{
    public int Compare(object x, object y)
    {
        var a = x as ArrayList;
        var b = y as ArrayList;
        // check for null if you need to!
        return a.Count.CompareTo(b.Count);
    }
}

However, unless you're actually using .NET 1.1, I'd recommend that you use List<T> instead of ArrayList, and the LINQ OrderBy method. This is type-safe, and I'd consider it more idiomatic C# nowadays. On top of that, it's way shorter:

var typedList = new List<List<int>>();
var sortedList = typedList.OrderBy(i => i.Count).ToList();

Be aware that the former is an in-place sort (altering the original list), whereas the latter copies the result into a new list.

Answer 2

I'm not allowed to comment yet or else I would. C# contains a built in static method in the ArrayList class. It sorts using the QuickSort algorithm. You may want to give it a try and see if it helps.
Microsoft API Documentation ArrayList.Sort()