I want to show CC Number and it is stored in DB as MaskedCreditCardNumber
I am not sure how to decrypt that value.

I know there is a method _encryptionService.DecryptText but since everything is an interface I cannot just instantiate it and even if I do it is null so throwing Object reference not set to an instance of an object.

Same thing goes with
Nop.Services.Orders.IOrderService _orderService;
Nop.Core.IWorkContext _workContext;

I will appreciate if anyone can reply to this.