Найти номера 5 максимальных значений ObservableCollection

  ObservableCollection<LineDom> Collection2 = new ObservableCollection<LineDom>(Collection1.OrderByDescending(x => x).Take(5));

 ObservableCollection<LineDom> Collection2 = new ObservableCollection<LinesAll>(Collection1.OrderByDescending(x => x).Take(5));

CompareTo(A x, A y)
{
   int sum = x.Sum.CompareTo(y.Sum);
   return sum == 0 ? x.Name.CompareTo(y.Name) : sum;
}

ObservableCollection<LineDom> Collection2 = new ObservableCollection<LineDom>(Collection1.OrderByDescending(x => x.Summa1).Take(5));

ObservableCollection<LineDom> Collection2 = new ObservableCollection<LineDom>(Collection1.OrderByDescending(x => x.Summa2).Take(5));

ObservableCollection<LineDom> Collection2 = new ObservableCollection<LinesAll>(Collection1(x.SummaAll => x.Summa, x.FlagAll => x.Flag));

var q = from a in Collection1
        select new {X = a.Param1, Y = a.Param2};
foreach(var v in q)
   Console.WriteLine(q.X + " " + q.Y);

var q = from a in q

var q = from  Collection1
        select new {X =Collection1.Param1, Y = Collection1.Param2};

class MyClass
{
   public int Param1;
   public int Param2;
... 
}
...
MyClass[] Collection1 = new MyClass[100];
...
var q = from b in Collection1
        select new {X =Collection1.Param1, Y = Collection1.Param2};

   Method1.OrderByDescending(item => item.Summa)
                .Take(5)
                .ToList()
                .ForEach(item => item.Flag = 1);

class MyClass
{
   public int Param1;
   public int Param2;
... 
}
...
MyClass[] Collection1 = new MyClass[100];
...
var q = from b in Collection1
        select new {X = b.Param1, Y =b.Param2};