Gtd.Client.Region.RegisterDock C# (CSharp) Method

        public void RegisterDock(UserControl control, string key)
        {
            _container.Sync(() =>
                {
                    control.Visible = false;
                    control.Dock = DockStyle.Fill;
                    _container.Controls.Add(control);

                    _controls.Add(key, control);
                });
        }

 public void AttachTo(Region mainRegion)
 {
     _region = mainRegion;
     mainRegion.RegisterDock(this, "inbox");
 }