Runtime-extensible custom fields.

public interface IHasDynamicProperties
{
    IReadOnlyDictionary<string, string?> DynamicProperties { get; }

    void SetProperty(string jsonName, string? value);
    string? GetProperty(string jsonName);
    T? GetProperty<T>(string jsonName);
    bool HasProperty(string jsonName);
    void RemoveProperty(string jsonName);
}

public class Contact : AggregateRoot<ContactId>, IHasDynamicProperties
{
    private readonly Dictionary<string, string?> _dynamicProperties = new();

    public string Name { get; private set; }
    public string Email { get; private set; }

    // IHasDynamicProperties implementation
    public IReadOnlyDictionary<string, string?> DynamicProperties
        => _dynamicProperties;

    public void SetProperty(string jsonName, string? value)
        => _dynamicProperties[jsonName] = value;

    public string? GetProperty(string jsonName)
        => _dynamicProperties.GetValueOrDefault(jsonName);

    public T? GetProperty<T>(string jsonName) { /* type conversion */ }
    public bool HasProperty(string jsonName)
        => _dynamicProperties.ContainsKey(jsonName);
    public void RemoveProperty(string jsonName)
        => _dynamicProperties.Remove(jsonName);
}

// In your EF Core entity configuration
public class ContactConfiguration : IEntityTypeConfiguration<Contact>
{
    public void Configure(EntityTypeBuilder<Contact> builder)
    {
        builder.ToTable("Contacts");
        builder.HasKey(x => x.Id);

        // Maps _dynamicProperties to JSONB column "PropertiesData"
        builder.ConfigureDynamicProperties<Contact>();
    }
}

// Program.cs — Register Dynamic Properties
services.AddDynamicProperties(options =>
{
    // Assembly containing your domain aggregates
    options.DomainAssembly = typeof(Contact).Assembly;
});

// Program.cs — Map admin endpoints
app.MapGroup("/api/admin")
   .RequireAuthorization()
   .MapDynamicPropertyEndpoints();

<DynamicPropertyPanel
    Definitions="@_definitions"
    Groups="@_groups"
    Values="@_entity.DynamicProperties"
    OnValueChanged="HandlePropertyChanged"
    TwoColumns="true"
    Variant="Variant.Outlined"
    Color="Color.Light" />

@code {
    private void HandlePropertyChanged(PropertyValueChange change)
    {
        _entity.SetProperty(change.JsonName, change.Value);
    }
}

// Filter contacts by dynamic property "phone_number"
// and built-in pagination parameters
GET /api/contacts?phone_number=+49123&city=berlin&page=1&pageSize=25

// snake_case params → property filters (phone_number, city)
// camelCase params → built-in (page, pageSize)