使用结构或类作为参数

Question

I'm fairly new to C# and programming in general, hence why I'm asking this question.

I recently got my code reviewed by a colleague, and he stated that for the following method, I should use a class for some parameters.

public List<Items> DoSomething(List<OtherItems> someItems, int amountOfItems, 
    DbGeopgrahpy Location)
{ //More stuff, irrelevant to the question.

He pointed out that I should put the amountOfItems and Location in a class which would contain those values instead.

This method will be called from a controller which returns this data to the client.

Now my question is why ? I understand that it would improve readability (arguably imo), but is there any benefits to using classes as parameters? I think I can assume this would even impact performance negatively when you have to declare a class each time you want to call this method.

I also found that structs can be used this way, if this is a good practice, when should I use structs and when should I use classes?

Answer 1

One of the benefit of using DTO class as method argument instead of collection of parameters is a preventing signature modification of method in future. This may be useful for API public methods, for example, as allow you to modify API without breaking changes / method versioning.

Let's say you need to update/modify method and so you need to pass additional argument. If your method expect only one argument, that is class/struct, then you do not need to change the signature of method. Instead you just add additional property to your DTO class.

Answer 2

It´s more a design awareness I think. If the method expects too many parameters that can be encapsulated in another object then that is spotting that you might haven´t done a good object definition. Also, as your software begin to grows you will find that it is much better to try to group everything in classes so you and the people that works with you will find much easier to mantain that way.

//avoid
public void Checkout(string shippingName, string shippingCity, 
       string shippingSate, string shippingZip, string billingName, 
       string billingCity, string billingSate, string billingZip)
{

}  

//DO
public void Checkout(ShippingAddress shippingAddress,BillingAddress billingAddress)
{
}

As you see, the common properties have been grouped to a common class that groups them. You have to apply your criteria and do a good grouping.

Answer 3

检查此=>在类和结构之间进行选择

Answer 4

Personally, I find that if I have more than 3 or 4 parameters that are logically grouped (belong to the same sort of object or info), then I'll use a class.

This is very arbitrary like you are finding. Each person has their own set of rules as to when they want to use a class/struct.