Activity.Id Property 
Definition
Important
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Gets an identifier that is unique in the scope of the workflow definition.
public:
 property System::String ^ Id { System::String ^ get(); };
	public string Id { get; }
	member this.Id : string
	Public ReadOnly Property Id As String
	Property Value
An identifier that is unique in the scope of the workflow definition.
Remarks
Id is used in tracking and validation.