C#のイテレーターブロックでテキストファイルを１行ごと読み込み

あ    1
い   2
う   3

using System;
using System.IO;

namespace IteratorBlock01;

class Program
{
    static void Main()
    {
        using StreamReader reader = new (@".\input.txt");
        string? line;
        while ((line = reader.ReadLine()) is not null)
        {
            string[] values = line.Split("\t");
            foreach (string value in values)
            {
                Console.WriteLine(value);
            }
        }
    }
}

あ
1
い
2
う
3

using System;
using System.IO;

namespace IteratorBlock01;

class Program
{
    static public IEnumerable<string> ReadIterator(string filename)
    {
        using StreamReader reader = new (filename);
        string? line;
        while ((line = reader.ReadLine()) is not null)
        {
            yield return line;
        }
    }
    static void Main()
    {
        const string filename = @".\input.txt";

        foreach(string line in ReadIterator(filename))
        {
            string[] values = line.Split("\t");
            foreach (string value in values)
            {
                Console.WriteLine(value);
            }
        }
    }
}