c# - Linq Query to retrieve all objects with a max value

Question

Currently I have a List of objects in which I need to find all occurrences that have the maximum value.

Currently my solution to this has been:

Foo maxFoo = list.OrderByDescending(foo => foo.A).First();
List<Foo> maxFoos = new List<Foo>();

foreach(Foo foo in list) {
    if (foo.A.Equals(maxFoo.A)) {
        maxFoos.Add(foo);
    }
}

However I want to know if there is a way to do this in a single Linq expression.

All the resources I have read only refer to getting the max value for one object.

Note: For the time being, I want to know a solution which doesn't rely on MoreLinq

Sergey Kalinichenko · Accepted Answer · 2015-10-21 00:16:54Z

3

You can group by the property, then order the groups by key, and take the content of the first one, like this:

var res = list
    .GroupBy(item => item.A)
    .OrderByDescending(g => g.Key)
    .First()
    .ToList();

answered Oct 21, 2015 at 0:16

Sergey Kalinichenko

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HashPsi · Accepted Answer · 2015-10-21 00:17:11Z

2

You could group by A, order the group, and get the elements in the first group, which corresponds to the elements with the max value of A:

list
  .GroupBy(x => x.A)
  .OrderByDescending(grp=> grp.Key)
  .First()
  .Select(x => x);

answered Oct 21, 2015 at 0:17

HashPsi

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Enigmativity · Accepted Answer · 2015-10-21 00:17:13Z

1

This works:

var maxFoos =
    list
        .OrderByDescending(foo => foo.A)
        .GroupBy(foo => foo.A)
        .Take(1)
        .SelectMany(foo => foo)
        .ToList();

answered Oct 21, 2015 at 0:17

Enigmativity

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