You can mark a HashSet directly for serialization. SaintsField will internally use SaintsHashSet to serialize it.

It support serializable types, abstract class/struct types, and interface types as element type.

// Note the `partial`!
public partial class SerDictionaryExample : MonoBehaviour
{
    [SaintsSerialized]
    public HashSet<string> stringHashSet;
    [SaintsSerialized]
    public HashSet<IInterface1> refHashSet;
}