Method MaxItemsBy

| Edit this page

MaxItemsBy<TSource, TKey>(IEnumerable<TSource>, Func<TSource, TKey>)

Returns all of the items that share the maximum value of a sequence.

Declaration
public static IEnumerable<TSource> MaxItemsBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
Parameters
Type Name Description
IEnumerable<TSource> source

The source sequence.
Func<TSource, TKey> keySelector

A function to extract a key from an element.
Returns
Type Description
IEnumerable<TSource>

An IEnumerable<T> containing all of the items that share the maximum value.
Type Parameters
Name Description
TSource

Type of elements in the sequence.
TKey

Type of keys.
Remarks

This operator is a shortcut for DensePartialSortBy<TSource, TKey>(IEnumerable<TSource>, int, Func<TSource, TKey>, OrderByDirection) with a direction of Descending and a count of 1.

This method is implemented by using deferred execution. However, source will be consumed in it's entirety immediately when first element of the returned sequence is consumed.

Examples

The following code example demonstrates how to get the maximum items from a sequence using MaxItemsBy.

var sequence = new[]
{
    (cnt: 1, item: "A"),
    (cnt: 2, item: "B"),
    (cnt: 3, item: "C"),
    (cnt: 4, item: "D"),
    (cnt: 5, item: "E"),
    (cnt: 1, item: "a"),
    (cnt: 2, item: "b"),
    (cnt: 3, item: "c"),
    (cnt: 4, item: "d"),
    (cnt: 5, item: "e"),
}.AsEnumerable();

// Find the maximum items of the sequence
var result = sequence
    .MaxItemsBy(x => x.cnt);

Console.WriteLine(
    "[" +
    string.Join(", ", result) +
    "]");

// This code produces the following output:
// [(5, E), (5, e)]
Exceptions
Type Condition
ArgumentNullException

source is null.
| Edit this page

MaxItemsBy<TSource, TKey>(IEnumerable<TSource>, Func<TSource, TKey>, IComparer<TKey>?)

Returns all of the items that share the maximum value of a sequence.

Declaration
public static IEnumerable<TSource> MaxItemsBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IComparer<TKey>? comparer)
Parameters
Type Name Description
IEnumerable<TSource> source

The source sequence.
Func<TSource, TKey> keySelector

A function to extract a key from an element.
IComparer<TKey> comparer

A IComparer<T> to compare keys.
Returns
Type Description
IEnumerable<TSource>

An IEnumerable<T> containing all of the items that share the maximum value.
Type Parameters
Name Description
TSource

Type of elements in the sequence.
TKey

Type of keys.
Remarks

This operator is a shortcut for DensePartialSortBy<TSource, TKey>(IEnumerable<TSource>, int, Func<TSource, TKey>, IComparer<TKey>?, OrderByDirection) with a direction of Descending and a count of 1.

This method is implemented by using deferred execution. However, source will be consumed in it's entirety immediately when first element of the returned sequence is consumed.

Examples

The following code example demonstrates how to get the maximum items from a sequence using MaxItemsBy.

var sequence = new[]
{
    (cnt: 1, item: "A"),
    (cnt: 2, item: "B"),
    (cnt: 3, item: "C"),
    (cnt: 4, item: "D"),
    (cnt: 5, item: "E"),
    (cnt: 1, item: "a"),
    (cnt: 2, item: "b"),
    (cnt: 3, item: "c"),
    (cnt: 4, item: "d"),
    (cnt: 5, item: "e"),
}.AsEnumerable();

// Find the maximum items of the sequence
var result = sequence
    .MaxItemsBy(x => x.item, StringComparer.OrdinalIgnoreCase);

Console.WriteLine(
    "[" +
    string.Join(", ", result) +
    "]");

// This code produces the following output:
// [(5, E), (5, e)]
Exceptions
Type Condition
ArgumentNullException

source is null.