I would like to get a list of 3 objects within a query Link.
var listaPessoas = from i in this.Context.CreateObjectSet<listaPessoas>()
select i;
...
listaPessoas = listaPessoas .Where(x => x.Nome.Contains(filtro.Nome);
...
return listaPessoas;
However, in this return I would like to get only 3 objects (always random) inside elements in listaPessoas
Use a Random object to sort the list and Take method to limit the amount of items returned.
Random rnd = new Random();
listaPessoas = listaPessoas.OrderBy(p => rnd.Next()).Take(3).ToList();
As you want to do this in the bank, you will need something different. One way to do this is to sort by Guid , since it is not possible to know what is going to be generated, the ordering will be random.
listaPessoas.OrderBy(r => Guid.NewGuid()).Take(3).ToList();
This option is great because it does not significantly increase the size of query and its complexity.
Best way to use it is Fisher-Yates shuffle (algorithm to generate a random permutation of a finite sequence)
Create an extension:
public static class EnumerableExtensions
{
public static IEnumerable<T> Shuffle<T>(this IEnumerable<T> source)
{
return source.Shuffle(new Random());
}
public static IEnumerable<T> Shuffle<T>(this IEnumerable<T> source, Random rng)
{
if (source == null) throw new ArgumentNullException("source");
if (rng == null) throw new ArgumentNullException("rng");
return source.ShuffleIterator(rng);
}
private static IEnumerable<T> ShuffleIterator<T>(
this IEnumerable<T> source, Random rng)
{
List<T> buffer = source.ToList();
for (int i = 0; i < buffer.Count; i++)
{
int j = rng.Next(i, buffer.Count);
yield return buffer[j];
buffer[j] = buffer[i];
}
}
}
way to use:
listaPessoas = listaPessoas.Shuffle().Take(3);