// Iterating Asynchronously: How to use async & await with foreach in C#

// https://medium.com/@t.masonbarneydev/iterating-asynchronously-how-to-use-async-await-with-foreach-in-c-d7e6d21f89fa

​

using System;

using System.Collections.Generic;

using System.Threading.Tasks;

​

public class Program

{

    public static async void Main()

    {

        var input = new List<string> { "1", "2", "3", "4", "5"};

        await BadLoopAsync(input);

        await LoopAsync(input);

    }

    public static Task DoAsync(string Item)

    {

        Task.Delay(1000);

        Console.WriteLine("Item: {0}", Item);

        return Task.CompletedTask;

    }

    //Looping method

    public  static async Task BadLoopAsync(IEnumerable<string> thingsToLoop)

    {

        foreach (var thing in thingsToLoop)

        {

            await DoAsync(thing);

        }        

    }

​

    //Method to iterate over collection and await DoAsync method

    public static async Task LoopAsync(IEnumerable<string> thingsToLoop)

    {

        List<Task> listOfTasks = new List<Task>();

​

        foreach (var thing in thingsToLoop)

        {

            listOfTasks.Add(DoAsync(thing));

        }

​

        await Task.WhenAll(listOfTasks);

    }

}