C#•2y ago

✅ HashSet property with List backing field

Posting here instead of in #database because it's not really related to db-specific stuff. For reasons described vaguely here: https://github.com/npgsql/efcore.pg/issues/2301, I am looking to implement a HashSet<T> property with a List<T> backing field which updates appropriately as I add and remove objects from the publicly exposed HashSet<T>. example class:

public sealed class GlobalUser
{
    private List<Snowflake> _blacklistedHighlightUsers = null!;

    public HashSet<Snowflake> BlacklistedHighlightUsers
    {
        get { /* TODO */ }
        set { /* TODO */ }
    }
}

public sealed class GlobalUser
{
    private List<Snowflake> _blacklistedHighlightUsers = null!;

    public HashSet<Snowflake> BlacklistedHighlightUsers
    {
        get { /* TODO */ }
        set { /* TODO */ }
    }
}

I want the underlying list field to be updated every time I modify the public property. Is there a way to accomplish this without any of the following? - never calling Add/Remove/etc methods and instead manually re-assigning the BlacklistedHighlightUsers every time - implementing my own wrapper class which overrides the Add/Remove/etc methods to somehow write to this underlying list - giving up on doing this in the first place and using a public List<T> and tossing on .ToHashSet().ToList() or .Distinct().ToList() everywhere I go all are what I'd consider ugly, hacky solutions that I'm not a fan of as they either mean I am overcomplicating things or there really just is not a solution

3 Replies

Saber•2y ago

whats the point of the list backing field?

Kiel•2y ago

you can only specify an "array" value converter if your property type is List<T> or T[]. Any other property type will either a) not show the extension method due to constraints, or b) if you force the type conversion manually a error is produced at migration generation time. You can't (by default, at least) specify enumerable value conversions, as using HasPostgresArrayConversion is heavily encouraged instead. I may have found a solution to my problem accidentally while scrolling just a tiny bit further in their issues tab on GitHub searching for HasPostgresArrayConversion, which happens to be someone trying to do the exact same thing as me: https://github.com/npgsql/efcore.pg/issues/1927 so this may be a non issue lol

Accord•2y ago

Closed!

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✅ HashSet property with List backing field