阻止MDI窗口出现在窗口菜单列表中

您应该处理菜单项的DropDownOpening事件,并从列表中删除不需要的项。像这样的:

MenuStrip ms = new MenuStrip();
ToolStripMenuItem windowMenu = new ToolStripMenuItem("Window");
ms.MdiWindowListItem = windowMenu;

windowMenu.DropDownOpening += (sender, e) =>
        {
            if (windowMenu.DropDownItems.Count > 0)
                windowMenu.DropDownItems.RemoveAt(0);
        };

ms.Items.Add(windowMenu);
ms.Dock = DockStyle.Top;            
this.MainMenuStrip = ms;
this.Controls.Add(ms);