動作環境

Windows 8.1 Pro (64bit)
Microsoft Visual Studio 2017 Community
Sublime Text 2

関連

System.IO.Fileクラス

処理概要

save
- List<string>にてリスト化
- WriteAllLines()にて書出し
load
- ReadAllLines()にて読込み
- foearchで全項目表示
- インデックスで特定項目表示

code

MainWindow.xaml

<Window x:Class="_171114_t1200_fileWriteRead.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:_171114_t1200_fileWriteRead"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Button Name="B_fileIO" Width="100" Height="30" Content="file IO" Click="B_fileIO_Click"/>
    </Grid>
</Window>

MainWindow.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace _171114_t1200_fileWriteRead
{
    /// <summary>
    /// MainWindow.xaml の相互作用ロジック
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();            
        }

        private readonly string kFilename = "test_171114.txt";

        private void fileWrite()
        {
            var datlst = new List<string>();
            for (int loop = 0; loop < 10; loop++)
            {
                datlst.Add("3.141592, 2.7182");
            }
            System.IO.File.WriteAllLines(kFilename, datlst.ToArray());
        }
        private void fileRead()
        {
            // 1. read all lines
            var datlst = System.IO.File.ReadAllLines(kFilename);
            foreach(var elem in datlst)
            {
                Console.WriteLine(elem);
            }
            // 2. show specific line
            Console.WriteLine("--- [5] ---");
            Console.WriteLine(datlst[5]);
        }

        private void B_fileIO_Click(object sender, RoutedEventArgs e)
        {
            fileWrite();
            fileRead();
        }
    }
}