What is an example where OCP is violated?

Before (OCP Violation):

public class DiscountCalculator
{
public decimal CalculateDiscount(string customerType)
{
if (customerType == "Regular") return 10;
if (customerType == "Premium") return 20;
if (customerType == "VIP") return 30;
return 0;
}
}
If you need to support a new customer type, you must modify this method — violating OCP.

fter (OCP Compliant):

public interface IDiscountStrategy
{

decimal GetDiscount();

}
public class RegularCustomerDiscount : IDiscountStrategy
{
public decimal GetDiscount() => 10;
}
public class PremiumCustomerDiscount : IDiscountStrategy
{
public decimal GetDiscount() => 20;
}
public class VipCustomerDiscount : IDiscountStrategy
{
public decimal GetDiscount() => 30;
}

Now you can add new customer types without modifying existing code — just create a new

strategy.