Add Light/Dark theme switching mechanism

[hesamkal2009]

Summary

Adds light and dark theme support to Service Bus Explorer.

Changes

• Added View > Theme with Light and Dark options.
• Persisted the selected theme as a per-user setting.
• Restored the selected theme when the application starts.
• Added theme-aware rendering for custom UI components such as the message delete button.
• Updated the README with usage instructions and the current limitation.

Known limitation

Changing the theme currently restarts the application. This is intentional because some existing WinForms controls do not reliably repaint all of their child controls when the theme is changed dynamically.

The selected theme is persisted before the restart, so the application comes back using the newly selected theme.

A future improvement could apply the theme without restarting the application.

[ErikMogensen]

Thanks @hesamkal2009!

Please provide screenshots of some of the dialogs/windows in the app so we see how it looks like.

[hesamkal2009]

My pleasure, @ErikMogensen.

Sure, the Default/Light theme is intact; I just added the Dark theme. :)

It's not perfect by any means, but at least it saves my eyes when I work at night in a dark room.

[Copilot]

Copilot review overview

🟡 Changes recommended

Dark-theme rendering, restart argument handling, generated settings access, and control retention contain unresolved defects.

Review effort: Balanced
Findings: 4

Open (4)

• Disable automatic CheckOnClick toggling · New
• Preserve the generated Settings.Default accessor · New
• Prevent static theme dictionaries from retaining disposed controls · New
• Theme DataGridView row and alternating-row styles · New

What changed in this PR

Adds persistent light/dark theme selection with restart-based application.

Changes:

• Introduces centralized WinForms theme application and restoration.
• Adds theme selection, persistence, restart behavior, and themed custom rendering.
• Documents appearance options and adds parsing tests.

File	Description
ThemeManager.cs	Implements theme state and control styling.
DataGridViewDeleteButtonCell.cs	Adds theme-aware rendering.
Settings.settings	Defines the user theme setting.
Settings.Designer.cs	Exposes the generated setting.
Program.cs	Initializes theming at startup.
MainForm.cs	Adds theme menu and restart flow.
ThemeManagerTests.cs	Tests theme parsing.
README.md	Documents theme usage.

Files not reviewed (1)

• src/ServiceBusExplorer/Properties/Settings.Designer.cs: Generated file

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[hesamkal2009]

Hi @ErikMogensen!

Apologies if I shouldn't be tagging you directly—I wasn't sure who to tag, and since you kindly provided comments earlier, I thought I'd reach out to you. Sorry for any inconvenience, and thank you for your time!

I wanted to follow up on this PR, as I’ve addressed the previous issues/feedback. 🙂

[ErikMogensen]

@hesamkal2009, this is non-paid work on my free time so sometimes it takes time. That said, thanks for providing this PR 👍🏻 . Having a dark theme would be great.

I ran Claude Code on it and it had three issues with it. It is seems unlikely that any one of them would happen, but on the other hand they seem easy to fix so please fix them:

The review found 3 bugs in the theme switching implementation:

🔴 CRITICAL: Unhandled exception in Process.Start (MainForm.cs:385)

Process.Start() can throw multiple exception types (FileNotFoundException, Win32Exception, InvalidOperationException, OutOfMemoryException) when application restart fails. With no exception handling, if the restart fails (file not found, access denied, etc.), an unhandled exception crashes the app. The theme preference is saved but the restart won't occur, leaving users confused about whether the change took effect.

🟡 MEDIUM: Missing null check for viewToolStripMenuItem (MainForm.cs:350)

The code calls viewToolStripMenuItem.DropDownItems.Insert(2, themeMenuItem) without verifying the menu item isn't null. While InitializeComponent() should initialize it, there's no defensive check. A NullReferenceException would occur if the menu structure changes or initialization fails.

🔵 LOW: GetCurrentParent() return value not null-checked (MainForm.cs:364)

The code calls selectedItem.GetCurrentParent().Items without checking if GetCurrentParent() returns null. While unlikely based on WinForms guarantees, this could theoretically throw a NullReferenceException.

[hesamkal2009]

@hesamkal2009, this is non-paid work on my free time so sometimes it takes time. That said, thanks for providing this PR 👍🏻 . Having a dark theme would be great.

I ran Claude Code on it and it had three issues with it. It is seems unlikely that any one of them would happen, but on the other hand they seem easy to fix so please fix them:

The review found 3 bugs in the theme switching implementation:

🔴 CRITICAL: Unhandled exception in Process.Start (MainForm.cs:385)

Process.Start() can throw multiple exception types (FileNotFoundException, Win32Exception, InvalidOperationException, OutOfMemoryException) when application restart fails. With no exception handling, if the restart fails (file not found, access denied, etc.), an unhandled exception crashes the app. The theme preference is saved but the restart won't occur, leaving users confused about whether the change took effect.

🟡 MEDIUM: Missing null check for viewToolStripMenuItem (MainForm.cs:350)

The code calls viewToolStripMenuItem.DropDownItems.Insert(2, themeMenuItem) without verifying the menu item isn't null. While InitializeComponent() should initialize it, there's no defensive check. A NullReferenceException would occur if the menu structure changes or initialization fails.

🔵 LOW: GetCurrentParent() return value not null-checked (MainForm.cs:364)

The code calls selectedItem.GetCurrentParent().Items without checking if GetCurrentParent() returns null. While unlikely based on WinForms guarantees, this could theoretically throw a NullReferenceException.

Thank you, @ErikMogensen, for your feedback! I genuinely appreciate your dedication, as well as the efforts of all maintainers who help nurture free software and support the community.

I apologize if my previous comment caused any inconvenience. I wanted to mention it because there isn't an "Ask for re-review" button available on this PR.

I'll address the mentioned issues.
Wishing you a wonderful weekend!

[hesamkal2009]

I love what @larrycaw made in #902.
It looks nice and slick, and it doesn't require restarting the app. A logical decision, with the maintainers' approval, would be to abandon this PR and merge that PR.

[ErikMogensen]

Thanks @hesamkal2009! Happy that you compared the PRs. It is, of course, not a problem to close this PR.