Fix issue 14624: [PropertyGrid] FolderNameEditor does not use the modern FolderBrowserDialog

[SimonZhao888]

Fixes #14624

Proposed changes

• Update InitializeDialog(FolderBrowser) → InitializeDialog(FolderBrowserDialog)
• Refactoring Unit Tests - FolderNameEditorTests.cs

Customer Impact

• [PropertyGrid] FolderNameEditor use the modern FolderBrowserDialog

Regression?

• No

Risk

• Mini

Screenshots

Before

14624-before.mp4

After

14624.mp4

Test methodology

• Manual testing

Test environment(s)

• 11.0.100-preview.5.26227.104

[Copilot]

Pull request overview

This PR updates the WinForms design-time FolderNameEditor used by PropertyGrid so it uses System.Windows.Forms.FolderBrowserDialog (which supports the modern/Vista-style folder picker when AutoUpgradeEnabled is enabled), and adjusts related design-time editors and tests accordingly.

Changes:

• Replaced the legacy FolderNameEditor.FolderBrowser usage with FolderBrowserDialog, and updated returned path handling to use SelectedPath.
• Updated SelectedPathEditor / InitialDirectoryEditor overrides to match the new InitializeDialog signature.
• Refactored/updated unit + UI integration tests and adjusted shipped public API text for the signature change.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/System.Windows.Forms.Design/src/System/Windows/Forms/Design/FolderNameEditor.cs	Switches the editor implementation to FolderBrowserDialog and updates InitializeDialog signature.
src/System.Windows.Forms.Design/src/System/Windows/Forms/Design/SelectedPathEditor.cs	Updates override to configure the new dialog type.
src/System.Windows.Forms.Design/src/System/Windows/Forms/Design/InitialDirectoryEditor.cs	Updates override to configure the new dialog type.
src/System.Windows.Forms.Design/src/PublicAPI.Shipped.txt	Updates the shipped API entry for FolderNameEditor.InitializeDialog.
src/System.Windows.Forms.Design/tests/UnitTests/System/Windows/Forms/Design/FolderNameEditorTests.cs	Refactors unit tests around the new dialog type/signature.
src/test/integration/UIIntegrationTests/FolderNameEditorTests.cs	Updates UI integration test to use FolderBrowserDialog / SelectedPath.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[LeafShi1]

Thanks for the PR! I have a few concerns — see inline comments.

[SimonZhao888]

@KlausLoeffelmann we use the modern FolderBrowseDialog to replace the old Dialog, and as we cannot render a tabbed layout within the dialog's UI, and the descriptive information displayed on the old form is no longer applicable to the new one.
Older:

Modern Dialog:

I need to add a title to the dialog interface to indicate the corresponding attribute. Such as following:

and

Do you have any suggestions?