If AllowsVpcAndNonVpcInstanceMemberships is 'false', this field is blank. If AllowsVpcAndNonVpcInstanceMemberships is 'true' and this field
is blank, then this option group can be applied to both VPC and non-VPC instances. If this field contains a value, then this option group
can only be applied to instances that are in the VPC indicated by this field.

C# |
public string VpcId { get; set; }