Inside my control, I have:
ContextMenu = new ContextMenu();
ContextMenu.MenuItems.Add(new MenuItem(\"&Add Item\", onAddSpeaker));
ContextMenu.MenuItems.A
ContextMenu has a constructor which receives an array of MenuItem objects. Needless to say, you can't add a string to that array. You can however get a seperator by adding a new MenuItem("-"):
var contextMenu = new ContextMenu(new[]
{
timerMenuItem,
keypressMenuItem,
new MenuItem("-"), // Seperator
new MenuItem(text: "Exit", onClick: (sender, args) => Application.Exit())
});