static class SubFormExtensions{    internal static bool AttachTo(this Form subForm, Panel panel)    {        if (panel == null || subForm == null) return false;        subForm.FormBorderStyle = FormBorderStyle.None;        subForm.TopLevel = false;        subForm.ShowInTaskbar = false;        subForm.Show();        subForm.Dock = DockStyle.Fill;        panel.Controls.Add(subForm);    }}