Method While

While<TSource>(Func<bool>, IEnumerable<TSource>)

Generates an enumerable sequence by repeating a source sequence as long as the given loop condition holds.

Declaration

public static IEnumerable<TSource> While<TSource>(Func<bool> condition, IEnumerable<TSource> source)

Parameters

Type	Name	Description
Func<bool>	condition	Loop condition.
IEnumerable<TSource>	source	Sequence to repeat while the condition evaluates true.

Returns

Type	Description
IEnumerable<TSource>	Sequence generated by repeating the given sequence while the condition evaluates to true.

Type Parameters

Name	Description
TSource	Source sequence element type.

Remarks

condition is evaluated lazily, once at the start of each loop of source.

source is cached via Memoize<TSource>(IEnumerable<TSource>, bool), so that it is only iterated once during the first loop. Successive loops will enumerate the cache instead of source.

Examples

The following code example demonstrates how to repeat a sequence while a condition is true using While.

var sequence = Enumerable.Range(1, 2);

// Repeat a sequence while a condition is true
var count = 0;
var result = SuperEnumerable
    .While(
        () => count++ < 3,
        sequence);

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

// This code produces the following output:
// [1, 2, 1, 2, 1, 2]

Exceptions

Type	Condition
ArgumentNullException	condition or source is null.