Use IEntityTypeConfiguration with a base entity

Question

In EF Core 2.0, we have the ability to derive from IEntityTypeConfiguration for cleaner Fluent API mappings (source).

How can I extend this pattern to utili

Answer 1

Another approach if you dont want to repeat the column Definitions for all of your Models that inherit from the same base Entity like this:

protected override void OnModelCreating(ModelBuilder modelBuilder){
        modelBuilder.Entity()
            .Property(b => b.CreatedDateTime)
            .HasDefaultValueSql("CURRENT_TIMESTAMP ");

        modelBuilder.Entity()
            .Property(b => b.CreatedDateTime)
            .HasDefaultValueSql("CURRENT_TIMESTAMP ");
        // …

}

is to find all the Entites that inhert from the base Entity, loop over them and call the generic Method as shown below, in which the redundant Logic is placed:

protected override void OnModelCreating(ModelBuilder modelBuilder){
    foreach (Type type in GetEntityTypes(typeof(BaseEntity))){
        var method = SetGlobalQueryMethod.MakeGenericMethod(type);
        method.Invoke(this, new object[] { modelBuilder });
    }
}

static readonly MethodInfo SetGlobalQueryMethod = typeof(/*your*/Context)
    .GetMethods(BindingFlags.Public | BindingFlags.Instance)
    .Single(t => t.IsGenericMethod && t.Name == "SetGlobalQuery");

public void SetGlobalQuery(ModelBuilder builder) where T : BaseEntity{
    builder.Entity().Property(o => o.CreatedDateTime).HasDefaultValueSql("CURRENT_TIMESTAMP");
    // Additional Statements
}

For the "GetEntityTypes" Method you need the Nuget Package „Microsoft.Extensions.DependencyModel“

private static IList _entityTypeCache;
private static IList GetEntityTypes(Type type)
{
    if (_entityTypeCache != null && _entityTypeCache.First().BaseType == type)
    {
        return _entityTypeCache.ToList();
    }

    _entityTypeCache = (from a in GetReferencingAssemblies()
                        from t in a.DefinedTypes
                        where t.BaseType == type
                        select t.AsType()).ToList();

    return _entityTypeCache;
}

private static IEnumerable GetReferencingAssemblies()
{
    var assemblies = new List();
    var dependencies = DependencyContext.Default.RuntimeLibraries;

    foreach (var library in dependencies)
    {
        try
        {
            var assembly = Assembly.Load(new AssemblyName(library.Name));
            assemblies.Add(assembly);
        }
        catch (FileNotFoundException)
        { }
    }
    return assemblies;
}

Its a bit hacky in my opinion, but works fine for me!

The source with more details:

https://www.codingame.com/playgrounds/5514/multi-tenant-asp-net-core-4---applying-tenant-rules-to-all-enitites