reactive/Ix.NET/Source/System.Linq.Async/System/Linq/Operators/ToArray.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT License.
// See the LICENSE file in the project root for more information. 

using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

namespace System.Linq
{
    public static partial class AsyncEnumerable
    {
        /// <summary>
        /// Creates an array from an async-enumerable sequence.
        /// </summary>
        /// <typeparam name="TSource">The type of the elements in the source sequence.</typeparam>
        /// <param name="source">The source async-enumerable sequence to get an array of elements for.</param>
        /// <param name="cancellationToken">The optional cancellation token to be used for cancelling the sequence at any time.</param>
        /// <returns>An async-enumerable sequence containing a single element with an array containing all the elements of the source sequence.</returns>
        /// <exception cref="ArgumentNullException"><paramref name="source"/> is null.</exception>
        /// <remarks>The return type of this operator differs from the corresponding operator on IEnumerable in order to retain asynchronous behavior.</remarks>
        public static ValueTask<TSource[]> ToArrayAsync<TSource>(this IAsyncEnumerable<TSource> source, CancellationToken cancellationToken = default)
        {
            if (source == null)
                throw Error.ArgumentNull(nameof(source));

            if (source is IAsyncIListProvider<TSource> arrayProvider)
                return arrayProvider.ToArrayAsync(cancellationToken);

            return AsyncEnumerableHelpers.ToArray(source, cancellationToken);
        }
    }
}