public class DateBasedTaxFactory:ITaxFactory{Customer _customer;ITaxFactory _taxFactory;public DateBasedTaxFactory(Customer c, ITaxFactory cb){_customer = c;_taxFactory = cb;}public ITax GetTaxObject(){if (_customer.StateCode == "TX"&& DateTime.Now.Month == 4&& DateTime.Now.Day == 4)return new NoTax();elsereturn _taxFactory.GetTaxObject();}}

Customer cust = new Customer(){StateCode = "TX", County = "Travis", ZipCode = "78745"};DateBasedTaxFactory db = new DateBasedTaxFactory(cust, new CustomerBasedTaxFactory(cust));ITax tax = db.GetTaxObject();//test for no tax for a certain dateif(tax.CalculateTax(3m) != 0){throw new Exception("the value is supposed to be zero");}

public class DateBasedTaxFactory : ITaxFactory
{Customer _customer;ITaxFactory _taxFactory;DateTime _dt;public DateBasedTaxFactory(Customer c, ITaxFactory cb,DateTime dt){_customer = c;_taxFactory = cb;_dt = dt;}public ITax GetTaxObject(){if (_customer.StateCode == "TX" && _dt.Month == 4 && _dt.Day == 4){return new NoTax();}elsereturn _taxFactory.GetTaxObject();}
} 

Customer cust = new Customer(){StateCode = "TX",County ="Travis",ZipCode = "78745"};
DateBasedTaxFactory db = new DateBasedTaxFactory(cust, new CustomerBasedTaxFactory(cust),new DateTime(2001,4,4));
ITax tax = GetTaxObject();
//test for no tax for a certain date
if (tax.CalculateTax(3m) != 0)
{throw new Exception("the value is supposed to be zero");
}

public class Order
{List<OrderItem> _orderItems = new List<OrderItem>();public decimal CalculateTotal(Customer customer){decimal total = _orderItems.Sum((item)=>{return item.Cost * item.Quantity;});decimal tax;if (customer.StateCode == "TX")tax = total * .08m;else if (customer.StateCode == "FL")tax = total * .09m;elsetax = .03m;total = total + tax;return total;}
}

 public interface ITax{decimal CalculateTax(decimal total);}public class TXTax:ITax{public decimal CalculateTax(decimal total){return total * 0.08m;}}public class CustomerBasedTaxFactory:ITaxFactory{Customer _customer;static Dictionary<string, ITax> stateTaxObjects = new Dictionary<string, ITax>();static Dictionary<string, ITax> countyTaxObjects = new Dictionary<string, ITax>();public CustomerBasedTaxFactory(Customer customer){_customer = customer;}public ITax GetTaxObject(){ITax tax;if(!string.IsNullOrEmpty(_customer.County)){if (!countyTaxObjects.Keys.Contains(_customer.StateCode)){tax = (ITax)Activator.CreateInstance("Tax", "Solid.taxes." + _customer.County + "CountyTax");countyTaxObjects.Add(_customer.StateCode, tax);}elsetax = countyTaxObjects[_customer.StateCode];}else{if (!stateTaxObjects.Keys.Contains(_customer.StateCode)){tax = (ITax)Activator.CreateInstance("Tax", "Solid.taxes." + _customer.StateCode + "Tax");stateTaxObjects.Add(_customer.StateCode, tax);}elsetax = stateTaxObjects[_customer.StateCode];}return tax;}}