Option.Required Property 
Definition
Important
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Indicates whether the option is required when its parent command is invoked.
public:
 property bool Required { bool get(); void set(bool value); };
	public bool Required { get; set; }
	member this.Required : bool with get, set
	Public Property Required As Boolean
	Property Value
Remarks
When an option is required and its parent command is invoked without it, an error results.