WowUp/WowUp.WPF/Extensions/TaskExtensions.cs

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

namespace WowUp.WPF.Extensions
{
    public static class TaskExtensions
    {
        public static Task ForEachAsync<T>(this IEnumerable<T> source, int dop, Func<T, Task> body)
        {
            return Task.WhenAll(
                from partition in Partitioner.Create(source).GetPartitions(dop)
                select Task.Run(async delegate {
                    using (partition)
                        while (partition.MoveNext())
                            await body(partition.Current);
                }));
        }
    }
}