【C#/WinForms実践入門編(5)】社員管理アプリを作る ～CSV読み込みとDataGridView表示～

namespace EmployeeManager.Models
{
    public class Employee
    {
        public string Id { get; set; }
        public string Name { get; set; }
        public string Department { get; set; }
        public DateTime JoinDate { get; set; }

        public Employee(string id, string name, string department, DateTime joinDate)
        {
            Id = id;
            Name = name;
            Department = department;
            JoinDate = joinDate;
        }

        //  CSVの1行から社員インスタンスを作成
        public static Employee FromCsv(string csvLine)
        {
            string[] values = csvLine.Split(',');
            return new Employee(
                values[ 0 ], values[ 1 ], values[ 2 ], DateTime.Parse(values[ 3 ])
            );
        }
    }
}

using System.Text;
using EmployeeManager.Models;

namespace EmployeeManager.Services
{
    public class CsvService
    {
        public List<Employee> ReadCsv(string filePath)
        {
            var employees = new List<Employee>();

            using (var reader = new StreamReader(filePath, true))
            {
                // ヘッダーをスキップ
                reader.ReadLine();

                string line;
                while ((line = reader.ReadLine()) != null)
                {
                    if (!string.IsNullOrWhiteSpace(line))
                    {
                        employees.Add(Employee.FromCsv(line));
                    }
                }
            }

            return employees;
        }
    }
}

using EmployeeManager.Services;

namespace EmployeeManager.Forms
{
    public partial class MainForm : Form
    {
        private readonly CsvService _csvService;

        public MainForm()
        {
            InitializeComponent();
            _csvService = new CsvService();
        }

        private void loadCsvButton_Click(object sender, EventArgs e)
        {
            using (OpenFileDialog dialog = new OpenFileDialog())
            {
                dialog.Filter = "CSVファイル|*.csv";
                if (dialog.ShowDialog() == DialogResult.OK)
                {
                    try
                    {
                        var employees = _csvService.ReadCsv(dialog.FileName);
                        employeeDataGridView.DataSource = employees;
                        MessageBox.Show("CSVファイルを読み込みました。", "成功",
                            MessageBoxButtons.OK, MessageBoxIcon.Information);
                    }
                    catch (Exception ex)
                    {
                        MessageBox.Show($"エラーが発生しました：{ex.Message}", "エラー",
                            MessageBoxButtons.OK, MessageBoxIcon.Error);
                    }
                }
            }
        }
    }
}

社員ID,氏名,部署,入社日
EMP001,山田太郎,営業部,2020/04/01
EMP002,鈴木花子,総務部,2019/04/01
EMP003,佐藤健一,開発部,2021/04/01
EMP004,田中美咲,営業部,2022/04/01
EMP005,伊藤博,人事部,2018/04/01
EMP006,渡辺明子,開発部,2020/10/01
EMP007,中村剛,営業部,2021/07/01
EMP008,小林優子,総務部,2019/10/01
EMP009,加藤正樹,開発部,2022/01/01
EMP010,吉田真理,人事部,2020/07/01