|
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;
namespace System.Linq
{
public static partial class AsyncEnumerable
{
/// <summary>
/// Projects each element of a sequence to an <see cref="IEnumerable{T}"/> and
/// flattens the resulting sequences into one <see cref="IAsyncEnumerable{T}"/> sequence.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TResult">The type of the elements of the sequence returned by selector.</typeparam>
/// <param name="source">A sequence of values to project.</param>
/// <param name="selector">A transform function to apply to each element.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> whose elements are the result of
/// invoking the one-to-many transform function on each element of the input sequence.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="selector"/> is <see langword="null"/>.</exception>
public static IAsyncEnumerable<TResult> SelectMany<TSource, TResult>(
this IAsyncEnumerable<TSource> source,
Func<TSource, IEnumerable<TResult>> selector)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(selector);
return Impl(source, selector, default);
async static IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TSource> source,
Func<TSource, IEnumerable<TResult>> selector,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
await foreach (TSource element in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
foreach (TResult subElement in selector(element))
{
yield return subElement;
}
}
}
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IEnumerable{T}"/> and
/// flattens the resulting sequences into one <see cref="IAsyncEnumerable{T}"/> sequence.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TResult">The type of the elements of the sequence returned by selector.</typeparam>
/// <param name="source">A sequence of values to project.</param>
/// <param name="selector">A transform function to apply to each element.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> whose elements are the result of
/// invoking the one-to-many transform function on each element of the input sequence.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="selector"/> is <see langword="null"/>.</exception>
public static IAsyncEnumerable<TResult> SelectMany<TSource, TResult>(
this IAsyncEnumerable<TSource> source,
Func<TSource, CancellationToken, ValueTask<IEnumerable<TResult>>> selector)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(selector);
return Impl(source, selector, default);
async static IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TSource> source,
Func<TSource, CancellationToken, ValueTask<IEnumerable<TResult>>> selector,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
await foreach (TSource element in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
foreach (TResult subElement in await selector(element, cancellationToken).ConfigureAwait(false))
{
yield return subElement;
}
}
}
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IAsyncEnumerable{T}"/> and
/// flattens the resulting sequences into one <see cref="IAsyncEnumerable{T}"/> sequence.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TResult">The type of the elements of the sequence returned by selector.</typeparam>
/// <param name="source">A sequence of values to project.</param>
/// <param name="selector">A transform function to apply to each element.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> whose elements are the result of
/// invoking the one-to-many transform function on each element of the input sequence.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="selector"/> is <see langword="null"/>.</exception>
public static IAsyncEnumerable<TResult> SelectMany<TSource, TResult>(
this IAsyncEnumerable<TSource> source,
Func<TSource, IAsyncEnumerable<TResult>> selector)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(selector);
return Impl(source, selector, default);
async static IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TSource> source,
Func<TSource, IAsyncEnumerable<TResult>> selector,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
await foreach (TSource element in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
await foreach (TResult subElement in selector(element).WithCancellation(cancellationToken).ConfigureAwait(false))
{
yield return subElement;
}
}
}
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IEnumerable{T}"/> and
/// flattens the resulting sequences into one <see cref="IAsyncEnumerable{T}"/> sequence.
/// The index of each source element is used in the projected form of that element.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TResult">The type of the elements of the sequence returned by selector.</typeparam>
/// <param name="source">A sequence of values to project.</param>
/// <param name="selector">A transform function to apply to each element.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> whose elements are the result of
/// invoking the one-to-many transform function on each element of the input sequence.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="selector"/> is <see langword="null"/>.</exception>
public static IAsyncEnumerable<TResult> SelectMany<TSource, TResult>(
this IAsyncEnumerable<TSource> source,
Func<TSource, int, IEnumerable<TResult>> selector)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(selector);
return Impl(source, selector, default);
async static IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TSource> source,
Func<TSource, int, IEnumerable<TResult>> selector,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
int index = -1;
await foreach (TSource element in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
foreach (TResult subElement in selector(element, checked(++index)))
{
yield return subElement;
}
}
}
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IEnumerable{T}"/> and
/// flattens the resulting sequences into one <see cref="IAsyncEnumerable{T}"/> sequence.
/// The index of each source element is used in the projected form of that element.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TResult">The type of the elements of the sequence returned by selector.</typeparam>
/// <param name="source">A sequence of values to project.</param>
/// <param name="selector">A transform function to apply to each element.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> whose elements are the result of
/// invoking the one-to-many transform function on each element of the input sequence.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="selector"/> is <see langword="null"/>.</exception>
public static IAsyncEnumerable<TResult> SelectMany<TSource, TResult>(
this IAsyncEnumerable<TSource> source,
Func<TSource, int, CancellationToken, ValueTask<IEnumerable<TResult>>> selector)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(selector);
return Impl(source, selector, default);
async static IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TSource> source,
Func<TSource, int, CancellationToken, ValueTask<IEnumerable<TResult>>> selector,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
int index = -1;
await foreach (TSource element in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
foreach (TResult subElement in await selector(element, checked(++index), cancellationToken).ConfigureAwait(false))
{
yield return subElement;
}
}
}
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IAsyncEnumerable{T}"/> and
/// flattens the resulting sequences into one <see cref="IAsyncEnumerable{T}"/> sequence.
/// The index of each source element is used in the projected form of that element.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TResult">The type of the elements of the sequence returned by selector.</typeparam>
/// <param name="source">A sequence of values to project.</param>
/// <param name="selector">A transform function to apply to each element.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> whose elements are the result of
/// invoking the one-to-many transform function on each element of the input sequence.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="selector"/> is <see langword="null"/>.</exception>
public static IAsyncEnumerable<TResult> SelectMany<TSource, TResult>(
this IAsyncEnumerable<TSource> source,
Func<TSource, int, IAsyncEnumerable<TResult>> selector)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(selector);
return Impl(source, selector, default);
async static IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TSource> source,
Func<TSource, int, IAsyncEnumerable<TResult>> selector,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
int index = -1;
await foreach (TSource element in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
await foreach (TResult subElement in selector(element, checked(++index)).WithCancellation(cancellationToken).ConfigureAwait(false))
{
yield return subElement;
}
}
}
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IEnumerable{T}"/>,
/// flattens the resulting sequences into one <see cref="IAsyncEnumerable{T}"/> sequence,
/// and invokes a result selector function on each element therein. The index of each source element is used in
/// the intermediate projected form of that element.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TCollection">The type of the intermediate elements collected by <paramref name="collectionSelector"/>.</typeparam>
/// <typeparam name="TResult">The type of the elements of the resulting sequence.</typeparam>
/// <param name="source">A sequence of values to project.</param>
/// <param name="collectionSelector">A transform function to apply to each element of the input sequence.</param>
/// <param name="resultSelector">A transform function to apply to each element of the intermediate sequence.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> whose elements are the result of
/// invoking the one-to-many transform function <paramref name="collectionSelector"/> on each element
/// of source and then mapping each of those sequence elements and their corresponding
/// source element to a result element.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="collectionSelector"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="resultSelector"/> is <see langword="null"/>.</exception>
public static IAsyncEnumerable<TResult> SelectMany<TSource, TCollection, TResult>(
this IAsyncEnumerable<TSource> source,
Func<TSource, IEnumerable<TCollection>> collectionSelector,
Func<TSource, TCollection, TResult> resultSelector)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(collectionSelector);
ThrowHelper.ThrowIfNull(resultSelector);
return Impl(source, collectionSelector, resultSelector, default);
async static IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TSource> source,
Func<TSource, IEnumerable<TCollection>> collectionSelector,
Func<TSource, TCollection, TResult> resultSelector,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
await foreach (TSource element in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
foreach (TCollection subElement in collectionSelector(element))
{
yield return resultSelector(element, subElement);
}
}
}
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IEnumerable{T}"/>,
/// flattens the resulting sequences into one <see cref="IAsyncEnumerable{T}"/> sequence,
/// and invokes a result selector function on each element therein. The index of each source element is used in
/// the intermediate projected form of that element.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TCollection">The type of the intermediate elements collected by <paramref name="collectionSelector"/>.</typeparam>
/// <typeparam name="TResult">The type of the elements of the resulting sequence.</typeparam>
/// <param name="source">A sequence of values to project.</param>
/// <param name="collectionSelector">A transform function to apply to each element of the input sequence.</param>
/// <param name="resultSelector">A transform function to apply to each element of the intermediate sequence.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> whose elements are the result of
/// invoking the one-to-many transform function <paramref name="collectionSelector"/> on each element
/// of source and then mapping each of those sequence elements and their corresponding
/// source element to a result element.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="collectionSelector"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="resultSelector"/> is <see langword="null"/>.</exception>
public static IAsyncEnumerable<TResult> SelectMany<TSource, TCollection, TResult>(
this IAsyncEnumerable<TSource> source,
Func<TSource, CancellationToken, ValueTask<IEnumerable<TCollection>>> collectionSelector,
Func<TSource, TCollection, CancellationToken, ValueTask<TResult>> resultSelector)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(collectionSelector);
ThrowHelper.ThrowIfNull(resultSelector);
return Impl(source, collectionSelector, resultSelector, default);
async static IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TSource> source,
Func<TSource, CancellationToken, ValueTask<IEnumerable<TCollection>>> collectionSelector,
Func<TSource, TCollection, CancellationToken, ValueTask<TResult>> resultSelector,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
await foreach (TSource element in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
foreach (TCollection subElement in await collectionSelector(element, cancellationToken).ConfigureAwait(false))
{
yield return await resultSelector(element, subElement, cancellationToken).ConfigureAwait(false);
}
}
}
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IAsyncEnumerable{T}"/>,
/// flattens the resulting sequences into one <see cref="IAsyncEnumerable{T}"/> sequence,
/// and invokes a result selector function on each element therein. The index of each source element is used in
/// the intermediate projected form of that element.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TCollection">The type of the intermediate elements collected by <paramref name="collectionSelector"/>.</typeparam>
/// <typeparam name="TResult">The type of the elements of the resulting sequence.</typeparam>
/// <param name="source">A sequence of values to project.</param>
/// <param name="collectionSelector">A transform function to apply to each element of the input sequence.</param>
/// <param name="resultSelector">A transform function to apply to each element of the intermediate sequence.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> whose elements are the result of
/// invoking the one-to-many transform function <paramref name="collectionSelector"/> on each element
/// of source and then mapping each of those sequence elements and their corresponding
/// source element to a result element.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="collectionSelector"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="resultSelector"/> is <see langword="null"/>.</exception>
public static IAsyncEnumerable<TResult> SelectMany<TSource, TCollection, TResult>( // satisfies the C# query-expression pattern
this IAsyncEnumerable<TSource> source,
Func<TSource, IAsyncEnumerable<TCollection>> collectionSelector,
Func<TSource, TCollection, TResult> resultSelector)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(collectionSelector);
ThrowHelper.ThrowIfNull(resultSelector);
return Impl(source, collectionSelector, resultSelector, default);
async static IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TSource> source,
Func<TSource, IAsyncEnumerable<TCollection>> collectionSelector,
Func<TSource, TCollection, TResult> resultSelector,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
await foreach (TSource element in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
await foreach (TCollection subElement in collectionSelector(element).WithCancellation(cancellationToken).ConfigureAwait(false))
{
yield return resultSelector(element, subElement);
}
}
}
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IAsyncEnumerable{T}"/>,
/// flattens the resulting sequences into one <see cref="IAsyncEnumerable{T}"/> sequence,
/// and invokes a result selector function on each element therein. The index of each source element is used in
/// the intermediate projected form of that element.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TCollection">The type of the intermediate elements collected by <paramref name="collectionSelector"/>.</typeparam>
/// <typeparam name="TResult">The type of the elements of the resulting sequence.</typeparam>
/// <param name="source">A sequence of values to project.</param>
/// <param name="collectionSelector">A transform function to apply to each element of the input sequence.</param>
/// <param name="resultSelector">A transform function to apply to each element of the intermediate sequence.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> whose elements are the result of
/// invoking the one-to-many transform function <paramref name="collectionSelector"/> on each element
/// of source and then mapping each of those sequence elements and their corresponding
/// source element to a result element.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="collectionSelector"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="resultSelector"/> is <see langword="null"/>.</exception>
public static IAsyncEnumerable<TResult> SelectMany<TSource, TCollection, TResult>(
this IAsyncEnumerable<TSource> source,
Func<TSource, IAsyncEnumerable<TCollection>> collectionSelector,
Func<TSource, TCollection, CancellationToken, ValueTask<TResult>> resultSelector)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(collectionSelector);
ThrowHelper.ThrowIfNull(resultSelector);
return Impl(source, collectionSelector, resultSelector, default);
async static IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TSource> source,
Func<TSource, IAsyncEnumerable<TCollection>> collectionSelector,
Func<TSource, TCollection, CancellationToken, ValueTask<TResult>> resultSelector,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
await foreach (TSource element in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
await foreach (TCollection subElement in collectionSelector(element).WithCancellation(cancellationToken).ConfigureAwait(false))
{
yield return await resultSelector(element, subElement, cancellationToken).ConfigureAwait(false);
}
}
}
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IEnumerable{T}"/>,
/// flattens the resulting sequences into one <see cref="IAsyncEnumerable{T}"/> sequence,
/// and invokes a result selector function on each element therein.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TCollection">The type of the intermediate elements collected by <paramref name="collectionSelector"/>.</typeparam>
/// <typeparam name="TResult">The type of the elements of the resulting sequence.</typeparam>
/// <param name="source">A sequence of values to project.</param>
/// <param name="collectionSelector">A transform function to apply to each element of the input sequence.</param>
/// <param name="resultSelector">A transform function to apply to each element of the intermediate sequence.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> whose elements are the result of
/// invoking the one-to-many transform function <paramref name="collectionSelector"/> on each element
/// of source and then mapping each of those sequence elements and their corresponding
/// source element to a result element.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="collectionSelector"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="resultSelector"/> is <see langword="null"/>.</exception>
public static IAsyncEnumerable<TResult> SelectMany<TSource, TCollection, TResult>(
this IAsyncEnumerable<TSource> source,
Func<TSource, int, IEnumerable<TCollection>> collectionSelector,
Func<TSource, TCollection, TResult> resultSelector)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(collectionSelector);
ThrowHelper.ThrowIfNull(resultSelector);
return Impl(source, collectionSelector, resultSelector, default);
static async IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TSource> source,
Func<TSource, int, IEnumerable<TCollection>> collectionSelector,
Func<TSource, TCollection, TResult> resultSelector,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
int index = -1;
await foreach (TSource element in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
foreach (TCollection subElement in collectionSelector(element, checked(++index)))
{
yield return resultSelector(element, subElement);
}
}
}
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IEnumerable{T}"/>,
/// flattens the resulting sequences into one <see cref="IAsyncEnumerable{T}"/> sequence,
/// and invokes a result selector function on each element therein.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TCollection">The type of the intermediate elements collected by <paramref name="collectionSelector"/>.</typeparam>
/// <typeparam name="TResult">The type of the elements of the resulting sequence.</typeparam>
/// <param name="source">A sequence of values to project.</param>
/// <param name="collectionSelector">A transform function to apply to each element of the input sequence.</param>
/// <param name="resultSelector">A transform function to apply to each element of the intermediate sequence.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> whose elements are the result of
/// invoking the one-to-many transform function <paramref name="collectionSelector"/> on each element
/// of source and then mapping each of those sequence elements and their corresponding
/// source element to a result element.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="collectionSelector"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="resultSelector"/> is <see langword="null"/>.</exception>
public static IAsyncEnumerable<TResult> SelectMany<TSource, TCollection, TResult>(
this IAsyncEnumerable<TSource> source,
Func<TSource, int, CancellationToken, ValueTask<IEnumerable<TCollection>>> collectionSelector,
Func<TSource, TCollection, CancellationToken, ValueTask<TResult>> resultSelector)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(collectionSelector);
ThrowHelper.ThrowIfNull(resultSelector);
return Impl(source, collectionSelector, resultSelector, default);
static async IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TSource> source,
Func<TSource, int, CancellationToken, ValueTask<IEnumerable<TCollection>>> collectionSelector,
Func<TSource, TCollection, CancellationToken, ValueTask<TResult>> resultSelector,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
int index = -1;
await foreach (TSource element in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
foreach (TCollection subElement in await collectionSelector(element, checked(++index), cancellationToken).ConfigureAwait(false))
{
yield return await resultSelector(element, subElement, cancellationToken).ConfigureAwait(false);
}
}
}
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IAsyncEnumerable{T}"/>,
/// flattens the resulting sequences into one <see cref="IAsyncEnumerable{T}"/> sequence,
/// and invokes a result selector function on each element therein.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TCollection">The type of the intermediate elements collected by <paramref name="collectionSelector"/>.</typeparam>
/// <typeparam name="TResult">The type of the elements of the resulting sequence.</typeparam>
/// <param name="source">A sequence of values to project.</param>
/// <param name="collectionSelector">A transform function to apply to each element of the input sequence.</param>
/// <param name="resultSelector">A transform function to apply to each element of the intermediate sequence.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> whose elements are the result of
/// invoking the one-to-many transform function <paramref name="collectionSelector"/> on each element
/// of source and then mapping each of those sequence elements and their corresponding
/// source element to a result element.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="collectionSelector"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="resultSelector"/> is <see langword="null"/>.</exception>
public static IAsyncEnumerable<TResult> SelectMany<TSource, TCollection, TResult>(
this IAsyncEnumerable<TSource> source,
Func<TSource, int, IAsyncEnumerable<TCollection>> collectionSelector,
Func<TSource, TCollection, CancellationToken, ValueTask<TResult>> resultSelector)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(collectionSelector);
ThrowHelper.ThrowIfNull(resultSelector);
return Impl(source, collectionSelector, resultSelector, default);
static async IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TSource> source,
Func<TSource, int, IAsyncEnumerable<TCollection>> collectionSelector,
Func<TSource, TCollection, CancellationToken, ValueTask<TResult>> resultSelector,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
int index = -1;
await foreach (TSource element in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
await foreach (TCollection subElement in collectionSelector(element, checked(++index)).WithCancellation(cancellationToken).ConfigureAwait(false))
{
yield return await resultSelector(element, subElement, cancellationToken).ConfigureAwait(false);
}
}
}
}
}
}
|