親フォルダ
01.using System;
02.using System.IO;
03.using System.Text;
04.using System.Windows.Forms;
05. 
06.namespace text_input_all
07.{
08.    class Program
09.    {
10.        [STAThread]
11.        static void Main(string[] args)
12.        {
13. 
14.            OpenFileDialog openFileDialog = new OpenFileDialog();
15.            openFileDialog.Filter = "テキスト|*.txt|全て|*.*";
16.            openFileDialog.FilterIndex = 2;
17.            openFileDialog.InitialDirectory = @"C:\";
18. 
19.            if (openFileDialog.ShowDialog() != DialogResult.OK)
20.            {
21.                return;
22.            }
23. 
24.            Console.WriteLine(openFileDialog.FileName);
25. 
26.            string path = openFileDialog.FileName;
27.            if ( File.Exists(path) )
28.            {
29.                Console.WriteLine($"{path} は存在しています" );
30.            }
31. 
32.            // SHIFT_JIS
33.            Encoding Enc = Encoding.GetEncoding(932);
34. 
35.            try
36.            {
37.                using (StreamReader ReadFile = new StreamReader(path, Enc))
38.                {
39.                    // 読込み
40.                    string Text = ReadFile.ReadToEnd();
41. 
42.                    // 全て読み込んでいるので閉じる
43.                    ReadFile.Close();
44. 
45.                    Console.WriteLine(Text);
46.                }
47. 
48.            }
49.            catch (Exception ex)
50.            {
51.                Console.WriteLine(ex.Message);
52.            }
53. 
54.            Console.ReadLine();
55.        }
56.    }
57.}