Question

I have the following example code. Waht is the best practice? Compare Values or compare Types to perform a certain business logic:

public Customer
{
    public Category {get;set;}
    public CategoryName {get;set;}  //e.g. "Category A" or "Category B"
}

public Category{}

public CategoryA : Category {}

public CategoryB : Category {}

public void Main()
{
    Customer customer = new Customer();

// Option 1:
if(customer.CategoryName == "Category A")
{
    CategoryA catA= customer.Category as CategoryA;     
    DoSomething(catA)
}

// Option 2:
CategoryA catA= customer.Category as CategoryA;
if(catA != null)
{
    DoSomething(catA)
}

// Option 3:
if(customer.Catgeory is Category A)
{
    CatgeoryA catA= customer.Category as CategoryA;
    DoSomething(catA)
}
}

The Code is just for illustration.

Answer 1

Given those 3 options, I’d go with Option 2.
e.g. – Try to make a conversion and check if it isn’t Null.

The reason it is better then the last option is that Option 3 causes you to make 2 conversions, one for the is and one for the as in the next line.

Finally, Option 1 is the worst IMO – it requires you to have some kind of logic that you can’t really be sure will stick later on (No one is preventing someone from creating a customer with a Category of CategoryA and a CategoryName of “Category B”). Also, this is additional logic which can be done in a much clearer way via Option 2.

I should mention, as pointed out in the other comments/answers, there are a few more options that can be taken into account. Using Polymorphism is probably the best design strategy.