Method Choose

Choose<T, TResult>(IEnumerable<T>, Func<T, (bool, TResult)>)

Applies a function to each element of the source sequence and returns a new sequence of result elements for source elements where the function returns a couple (2-tuple) having a true as its first element and result as the second.

Declaration

public static IEnumerable<TResult> Choose<T, TResult>(this IEnumerable<T> source, Func<T, (bool, TResult)> chooser)

Parameters

Type	Name	Description
IEnumerable<T>	source	The source sequence.
Func<T, (bool, TResult)>	chooser	The function that is applied to each source element.

Returns

Type	Description
IEnumerable<TResult>	A sequence TResult elements.

Type Parameters

Name	Description
T	The type of the elements in source.
TResult	The type of the elements in the returned sequence.

Remarks

This method uses deferred execution semantics and streams its results.

Examples

The following code example demonstrates choose and project elements in a sequence using the Choose operator.

var sequence = "O,l,2,3,4,S,6,7,B,9".Split(','); 

// Use a function to choose and project elements in the sequence
var result = sequence
    .Choose(s => (int.TryParse(s, out var n), n));

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

// This code produces the following output:
// [2, 3, 4, 6, 7, 9]

Exceptions

Type	Condition
ArgumentNullException	source or chooser is null.