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CSharp · Console

/Program.cs

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

public class Program
{
	public static void Main()
	{
		var source = new List<int>{ 1, 2, 3, 4, 5 };
		var source2 = new List<int>();
		
		var tasks = source.Select(x => Task.Run(() => Console.WriteLine(x)));
		var tasks2 = source2.Select(x => Task.Run(() => Console.WriteLine(x)));
		
		var res = Extensions.Append<Task>(tasks, tasks2);
		
		Console.WriteLine("Total tasks:" + res.Count());
		Task.WaitAll(res.ToArray());
		
		Console.WriteLine("Done");
	}
	
	public static class Extensions
	{
		public static IEnumerable<T> Append<T>(IEnumerable<T> source, IEnumerable<T> items)
		{			
			source.ToList().AddRange(items);
			return source;
		}
	}
}