reactive/Ix.NET/Source/System.Interactive/System/Linq/Operators/ForEach.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the Apache 2.0 License.
// See the LICENSE file in the project root for more information. 

using System.Collections.Generic;

namespace System.Linq
{
    public static partial class EnumerableEx
    {
        /// <summary>
        /// Enumerates the sequence and invokes the given action for each value in the sequence.
        /// </summary>
        /// <typeparam name="TSource">Source sequence element type.</typeparam>
        /// <param name="source">Source sequence.</param>
        /// <param name="onNext">Action to invoke for each element.</param>
        public static void ForEach<TSource>(this IEnumerable<TSource> source, Action<TSource> onNext)
        {
            if (source == null)
            {
                throw new ArgumentNullException(nameof(source));
            }

            if (onNext == null)
            {
                throw new ArgumentNullException(nameof(onNext));
            }

            foreach (var item in source)
            {
                onNext(item);
            }
        }

        /// <summary>
        /// Enumerates the sequence and invokes the given action for each value in the sequence.
        /// </summary>
        /// <typeparam name="TSource">Source sequence element type.</typeparam>
        /// <param name="source">Source sequence.</param>
        /// <param name="onNext">Action to invoke for each element.</param>
        public static void ForEach<TSource>(this IEnumerable<TSource> source, Action<TSource, int> onNext)
        {
            if (source == null)
            {
                throw new ArgumentNullException(nameof(source));
            }

            if (onNext == null)
            {
                throw new ArgumentNullException(nameof(onNext));
            }

            var i = 0;
            foreach (var item in source)
            {
                onNext(item, checked(i++));
            }
        }
    }
}