Setting ShowInTaskbar to false causes the form to close automatically (Abnormal exit).

Setting ShowInTaskbar to false causes the form to close automatically (Abnormal exit).

https://docs.microsoft.com/en-us/dotnet/api/system.windows.forms.form

Test Code: .NET 6.0 (Version: 6.0.1)(This problem also appears in .net framework 4.8) Win10 system (21H2).

using System;
using System.Windows.Forms;

namespace FormShowInTaskbarTest
{
    internal static class Program
    {
        private static Form form1;
        private static Form form2;

        [STAThread]
        static void Main()
        {
            ApplicationConfiguration.Initialize();

            form1 = new Form()
            {
                Width = 800,
                Height = 600,
                StartPosition = FormStartPosition.CenterScreen,
            };

            var button1 = new Button()
            {
                Text = "Click here to open new Form.",

                Width = 200,
                Height = 100,
            };

            button1.Click += Button1_Click;
            form1.Controls.Add(button1);

            Application.Run(form1);
        }

        private static void Button1_Click(object sender, EventArgs e)
        {
            form2 = new Form()
            {
                Width = 600,
                Height = 400,

                StartPosition = FormStartPosition.CenterScreen,
            };

            var button2 = new Button()
            {
                Text = "Click here to test ShowInTaskbar.",

                Width = 200,
                Height = 100,
            };

            button2.Click += Button2_Click;
            form2.Controls.Add(button2);

            form2.ShowDialog(form1);
        }

        private static void Button2_Click(object sender, EventArgs e)
        {
            form2.ShowInTaskbar = false;
        }
    }
}

Steps to reproduce:

1. Run the appliction.
2. Click the first button, the application will open a new Form.
3. Click the first button in new form.

[RussKie]

I have run the provided sample on Win11 (10.0.22000 Build 22000), and confirmed the behaviour is consistent as far as .NET Framework 4.7.2 and all the way up to .NET 7 Preview1.

@Olina-Zhang would you be able to test 6421.zip on different versions of Windows 10 and see if there are any differences in behaviours? Thank you.

[AraHaan]

Wait why is System.Private.Winforms preview 4 still?

Sad it don’t add an download link that links to the azureblobstorage location of them either.