C#•14mo ago

❔ ✅ Struct equality

hi! I have a struct such as this one:

public readonly struct InternerId
{
    private readonly int _id;

    internal InternerId(int id)
    {
        _id = id;
    }
}

public readonly struct InternerId
{
    private readonly int _id;

    internal InternerId(int id)
    {
        _id = id;
    }
}

What's the correct way to implement equality between two InternerIds based on _id? I don't want equality with any other type except itself.

27 Replies

Thinker•14mo ago

Override bool Equals(object? other) and optionally implement IEquatable<InternerId> You could also use a record struct, which implements equality by default

__dil__OP•14mo ago

I thought about this, but I'm not sure if/how that works with keeping the field private, the constructor internal, and the whole type public

Thinker•14mo ago

I guess

__dil__OP•14mo ago

Does that mean it's not possible? (sorry I'm not a native english speaker so it's not super clear what "I guess" means in this context 😅 )

Thinker•14mo ago

No I meant your point is valid as to why you shouldn't use a record here, my bad

__dil__OP•14mo ago

Ah ok I see. Thanks for the help 😄 I'll implement what you suggested 🙂

reflectronic•14mo ago

you can still use a record in fact, this would do what you want

public readonly record struct InternerId
{
    private readonly int _id;

    internal InternerId(int id)
    {
        _id = id;
    }
}

public readonly record struct InternerId
{
    private readonly int _id;

    internal InternerId(int id)
    {
        _id = id;
    }
}

__dil__OP•14mo ago

oh interesting! So, for the purpose of equality and such, records consider all their fields/properties?

reflectronic•14mo ago

the auto-generated equality is based on all the fields, right

__dil__OP•14mo ago

ok yeah, that's good to know definitely reduces boilerplate here thanks!

reflectronic•14mo ago

you can reduce the boilerplate even further with a primary constructor

public readonly record struct InternerId(int id)
{
    private readonly int id = id;
}

public readonly record struct InternerId(int id)
{
    private readonly int id = id;
}

when you assign a primary constructor parameter directly to a field or property with the same name, it prevents the public property from being generated it does sort of break the _ convention. i think it is a dumb convention and you will run into pitfalls like this if you try to stick with it. but that is just my strong opinion

__dil__OP•14mo ago

I think this is slightly different though since the constructor would also be public (instead of internal?

reflectronic•14mo ago

uh. oh

__dil__OP•14mo ago

but still really good to know nonetheless

reflectronic•14mo ago

well then ignore all of that

__dil__OP•14mo ago

I mean, it's still good to know in general but yeah

Thinker•14mo ago

is it?

reflectronic•14mo ago

yes this includes auto-generated backing fields, of course

MODiX•14mo ago

reflectronic

sharplab.io (click here)

public readonly record struct InternerId(int id) {
    private readonly int id = id;
}

public readonly record struct InternerId(int id) {
    private readonly int id = id;
}

Try the /sharplab command! | React with ❌ to remove this embed.

reflectronic•14mo ago

you can look at the implementation of Equals here to see what is going on

Thinker•14mo ago

ah thought it only looked at props

__dil__OP•14mo ago

So, just to be sure, for the purpose of the original question, this would be the way to go, right?

public readonly record struct InternerId
{
    private readonly int _id;

    internal InternerId(int id)
    {
        _id = id;
    }
}

public readonly record struct InternerId
{
    private readonly int _id;

    internal InternerId(int id)
    {
        _id = id;
    }
}

reflectronic•14mo ago

right

__dil__OP•14mo ago

Alright, thank you both 🙂 by the way, is there a way to mark the thread as "solved"? 🤔

reflectronic•14mo ago

$close

MODiX•14mo ago

Use the /close command to mark a forum thread as answered

Accord•14mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ ✅ Struct equality