UnionCollectionsHashSet

using System;
using System.Collections.Generic;

namespace CSLight
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] firstArray = ReadStringArray(' ');
            string[] secondArray = ReadStringArray(' ');
            HashSet<string> unionCollection = new HashSet<string>();
            AddRangeToCollection(unionCollection, firstArray);
            AddRangeToCollection(unionCollection, secondArray);

            Console.WriteLine("Итоговая коллекция: ");
            PrintCollection(unionCollection);
        }

        private static void AddRangeToCollection<T>(ICollection<T> originCollection, IList<T> addedCollection)
        {
            foreach (T addedElement in addedCollection)
            {
                originCollection.Add(addedElement);
            }
        }

        private static void PrintCollection<T>(ICollection<T> collection)
        {
            foreach (T element in collection)
            {
                Console.Write($"{element} ");
            }
            Console.WriteLine();
        }

        private static string[] ReadStringArray(char separator)
        {
            Console.WriteLine($"Введите массив через '{separator}'");
            string text = Console.ReadLine();
            string[] result = text.Split(separator);
            return result;
        }
    }
}