using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Threading.Tasks;

​

namespace v3 {

​

    class Program {

        static async Task Main(string[] args) {

            var w = new Worker();

            var links = await w.Start();

            Console.WriteLine("Uploaded to cloud files URLs:");

            foreach(var linkItem in links) {

                Console.WriteLine(linkItem);

            }

        }

​

    }

    class Worker {

        public async Task<IEnumerable<Uploaded>> Start() {

            await Task.Delay(0);

​

            var proc = new ImageProcessor();

            var resizedImages = proc.GetResizedImages("sourceFile.jpg");

​

            var tasks = new List<Task<Uploaded>>();

            foreach(var image in resizedImages) {

                var uploadTask = Task.Run(async () => await proc.UploadImage(image));

                tasks.Add(uploadTask);

            }

            await Task.WhenAll(tasks);

​

            return tasks.Select(x => x.Result);

        }

    }

​

    class ImageProcessor {

​

        public IEnumerable<Resized> GetResizedImages(string fileName) {

​

            for (var i = 0; i < 10; i++) {

                Console.WriteLine($"Start resize image {i}");

                /// Имитируем работу конвертора изображений

                var rand = new Random(DateTime.UtcNow.Millisecond);

                Task.Delay(rand.Next(100, 400)).Wait();

​

​

                yield return new Resized(i);

            }

            yield break;

        }

​

​

​

​

        public async Task<Uploaded> UploadImage(Resized image) {

            Console.WriteLine($"Start upload image {image.Index}");

            /// Имитируем работу загрузчика на облако

            var rand = new Random(DateTime.UtcNow.Millisecond);

            await Task.Delay(rand.Next(400, 700));

​

            return new Uploaded(image.Index);

        }

​

​

    }

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    class Resized {

        readonly int stream;

​

        public Resized(int index) {

            this.stream = index;

        }

​

        public int Index { get => stream; }

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        public override string ToString() {

            return $"{nameof(Resized)} file - STREAM: {stream}";

        }

    }

​

    class Uploaded {

        readonly int url;

​

        public Uploaded(int index) {

            this.url = index;

        }

​

        public int Index { get => url; }

​

        public override string ToString() {

            return $"{nameof(Uploaded)} file - URL: {url}";

        }

    }

}

​