dotnet/winforms

[DarkMode]The Form1 title bar change to white color after change the ShowInTaskbar property

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#12,992 opened on Feb 20, 2025

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area-DarkModehelp wanted

Description

.NET version

.NET 10.0.100-preview.2.25118.3

Did it work in .NET Framework?

No

Did it work in any of the earlier releases of .NET Core or .NET 5+?

No, also repro in .NET 9.0 which it started to be supported.

Issue description

The Form1 title bar change to white color after change the ShowInTaskbar property.

Image

Steps to reproduce

  1. Create a winforms .NET Core project with a button control.
  2. Enable DarkMode by Application.SetColorMode(SystemColorMode.Dark) in Program.cs file.
  3. Double click button control and add below code to button click event. `this.ShowInTaskbar = !this.ShowInTaskbar;
  4. Build and run.
  5. Click button control.

More Info:

  1. This issue also repro in FormShowinTaskbar test in WinformsControlTest app.

https://github.com/user-attachments/assets/92e54b94-a73b-4524-bec7-cfaef740d089

Contributor guide

Tech stack
csharp
Domain
desktop
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
C# basicsWindows FormsDark mode in WinForms
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
Investigate the Form's title bar rendering when ShowInTaskbar is toggled in dark mode. Look at the Form.ShowInTaskbar property setter and how it interacts with dark mode color settings. Also examine the FormShowinTaskbar test in the WinformsControlTest app for reproduction. Check if there are existing tests or code paths that handle title bar color updates.
[DarkMode]The Form1 title bar change to white color after change the ShowInTaskbar property · dotnet/winforms#12992 | Good First Issue