How to sort and list only 5 items from a list?

Question

You see, I am developing the Dashboard of a web system, in one of the filters I should list the 5 main customers and sort them by higher value of the sums of total of issued bills. I’m already able to quietly list, the problem is that the filter is listing everything (when it should just list 5) and is disorderly. Follow my code below:

public ActionResult Index()

        {
            var dashboard = new DashboardViewModel();


                var lista = new List<NotaFiscal>();


            var participantes = db.Participantes
                          .ToList();
            var notas = db.NotasFiscais
                          .ToList();

            foreach (var part in participantes)
            {
                var x = new NotaFiscal();
                var res = notas.Where(y => y.ClienteID == part.ParticipanteId).Sum(o => o.ValorTotalNota);
                x.ClienteID = part.ParticipanteId;
                x.ValorTotalNota = res;
                x.NomeCliente = part.NomeParticipante;
                lista.Add(x);
            }


            dashboard.NotasFiscais = lista;
            dashboard.NotasFiscais.Take(5).OrderByDescending(x => x.ValorTotalNota);
            return View(dashboard);
        }

Would someone point out to me the solution so that this filter lists only the 5 records with the highest amounts of bills?

Below Jean and Filipe gave me alternatives, after making the suggested in both cases occur the following error, see the image:

Answer 1

The filter was made but was not assigned again where it should

You can do it like this:

dashboard.NotasFiscais = lista.Take(5).OrderByDescending(x => x.ValorTotalNota);
return View(dashboard);

And you can change the code a little because of the queries, since when a toList is done, the query is executed and this can affect the performance of what you are implementing.

Here’s an example of what it might look like:

var dashboard = new DashboardViewModel();


var lista = dbParticipantes
    .Select(e => new NotaFiscal {  
        ClienteID = e.ParticipanteId,
        ValorTotalNota = e.NotasFiscais.Sum(n => n.ValorTotalNota)
    })
    .OrderByDescending(e => e.ValorTotalNota)
    .Take(5);

dashboard.NotasFiscais = lista;
return View(dashboard);

Answer 2

Explanation

The problem of your code that does not sort as expected is in the section below:

 dashboard.NotasFiscais.Take(5).OrderByDescending(x => x.ValorTotalNota);

We can see that before sorting, you select five records through the method Take(5). To make it work properly, change the order to the example below:

dashboard.NotasFiscais.OrderByDescending(x => x.ValorTotalNota).Take(5);

Suggestion

Change this code block:

   foreach (var part in participantes)
            {
                var x = new NotaFiscal();
                var res = notas.Where(y => y.ClienteID == part.ParticipanteId).Sum(o => o.ValorTotalNota);
                x.ClienteID = part.ParticipanteId;
                x.ValorTotalNota = res;
                x.NomeCliente = part.NomeParticipante;
                lista.Add(x);
            }

East:

var lista = db.NotasFiscais
                 .Where(x => db.Participantes.Any(y => y.ParticipanteID == x.ClienteID))
                 .GroupBy(z => z.ClienteID)
                 .Select(x => new NotaFiscal(){
                        ClienteID = x.First().ClienteID,
                        ValorTotalNota = x.Sum(n => n.ValorTotalNota)
                  })
                 .OrderByDescending(x => x.ValorTotalNota)
                 .Take(5)
                 .ToList();

dashboard.NotasFiscais = lista;
return View(dashboard);

_{See working on Ideone}