[C#] FolderBrowserDialogでデフォルトパスを設定する方法

folderBrowserDialog.RootFolder = Environment.SpecialFolder.MyDocuments; // マイドキュメントを基準に設定

folderBrowserDialog.SelectedPath = @"C:\Users\Username\Documents"; // 初期選択フォルダを設定

using System;
using System.Windows.Forms;
public partial class MyForm : Form
{
    public MyForm()
    {
        InitializeComponent();
        ShowFolderBrowserDialog();
    }
    private void ShowFolderBrowserDialog()
    {
        using (FolderBrowserDialog folderBrowserDialog = new FolderBrowserDialog())
        {
            // 基準フォルダをマイドキュメントに設定
            folderBrowserDialog.RootFolder = Environment.SpecialFolder.MyDocuments;
            // 初期選択フォルダを設定
            folderBrowserDialog.SelectedPath = @"C:\Users\Username\Documents";
            // ダイアログを表示
            if (folderBrowserDialog.ShowDialog() == DialogResult.OK)
            {
                // ユーザーが選択したフォルダのパスを取得
                string selectedPath = folderBrowserDialog.SelectedPath;
                MessageBox.Show("選択したフォルダ: " + selectedPath);
            }
        }
    }
}

using System;
using System.IO;
using System.Windows.Forms;
public partial class MyForm : Form
{
    private const string settingsFilePath = "settings.txt"; // 設定ファイルのパス
    public MyForm()
    {
        InitializeComponent();
        ShowFolderBrowserDialog();
    }
    private void ShowFolderBrowserDialog()
    {
        string lastSelectedPath = LoadLastSelectedPath(); // 前回選択したパスを読み込む
        using (FolderBrowserDialog folderBrowserDialog = new FolderBrowserDialog())
        {
            folderBrowserDialog.SelectedPath = lastSelectedPath; // 前回のパスを初期選択
            if (folderBrowserDialog.ShowDialog() == DialogResult.OK)
            {
                string selectedPath = folderBrowserDialog.SelectedPath;
                SaveLastSelectedPath(selectedPath); // 選択したパスを保存
                MessageBox.Show("選択したフォルダ: " + selectedPath);
            }
        }
    }
    private void SaveLastSelectedPath(string path)
    {
        File.WriteAllText(settingsFilePath, path); // 設定ファイルに保存
    }
    private string LoadLastSelectedPath()
    {
        return File.Exists(settingsFilePath) ? File.ReadAllText(settingsFilePath) : ""; // 設定ファイルから読み込み
    }
}

using System;
using System.Collections.Generic;
using System.Windows.Forms;
public partial class MyForm : Form
{
    public MyForm()
    {
        InitializeComponent();
        ShowMultiFolderSelectionDialog();
    }
    private void ShowMultiFolderSelectionDialog()
    {
        using (Form multiSelectForm = new Form())
        {
            CheckedListBox checkedListBox = new CheckedListBox();
            checkedListBox.Items.AddRange(new object[] { "C:\\Folder1", "C:\\Folder2", "C:\\Folder3" });
            checkedListBox.Dock = DockStyle.Fill;
            Button okButton = new Button() { Text = "OK", Dock = DockStyle.Bottom };
            okButton.Click += (sender, e) =>
            {
                List<string> selectedFolders = new List<string>();
                foreach (var item in checkedListBox.CheckedItems)
                {
                    selectedFolders.Add(item.ToString());
                }
                MessageBox.Show("選択したフォルダ: " + string.Join(", ", selectedFolders));
                multiSelectForm.Close();
            };
            multiSelectForm.Controls.Add(checkedListBox);
            multiSelectForm.Controls.Add(okButton);
            multiSelectForm.ShowDialog();
        }
    }
}

using System;
using System.Windows.Forms;
public partial class MyForm : Form
{
    public MyForm()
    {
        InitializeComponent();
        ShowCustomFolderSelection();
    }
    private void ShowCustomFolderSelection()
    {
        using (Form customDialog = new Form())
        {
            TreeView folderTreeView = new TreeView();
            folderTreeView.Dock = DockStyle.Fill;
            Button selectButton = new Button() { Text = "選択", Dock = DockStyle.Bottom };
            selectButton.Click += (sender, e) =>
            {
                string selectedPath = folderTreeView.SelectedNode?.FullPath;
                if (selectedPath != null)
                {
                    MessageBox.Show("選択したフォルダ: " + selectedPath);
                    customDialog.Close();
                }
            };
            customDialog.Controls.Add(folderTreeView);
            customDialog.Controls.Add(selectButton);
            customDialog.ShowDialog();
        }
    }
}