System.InvalidOperationException:“Operation is not valid due to the current state of the object.”

System.InvalidOperationException:“Operation is not valid due to the current state of the object.”
 CurrentWindow.Activate();
 ContextMenuItem menu = new ContextMenuItem
 {
     Title = "Open UF.Client Here",
     AcceptDirectory = true,
     Exe = "UF.Client.exe",
     Param = "{path}"
 };
 await new ContextMenuService().SaveAsync(menu);