c# - Populate Created and LastModified automagically in EF Core

Question

Looking forward to build a framework, (No repository pattern to working with DbSets directly) to autopopulate Created and last modified automatically, rather than spitting out these codes through out code base.

Could you point me out in right direction how to achieve it.

In past I tried populating these in constructors, however that seems like a nasty code and every time we pull up somting from database EF change tracking will mark the entity as modified.

.ctor()
    {
        Created = DateTime.Now;
        LastModified = DateTime.Now;
    }

public interface IHasCreationLastModified
    {
        DateTime Created { get; set; }
        DateTime? LastModified { get; set; }
    }

public class Account : IEntity, IHasCreationLastModified
{
    public long Id { get; set; }

    public DateTime Created { get; set; }
    public DateTime? LastModified { get; set; }
    public virtual IdentityUser IdentityUser { get; set; }
}

Answer 1

Starting with v2.1, EF Core provides State change events:

New Tracked And StateChanged events on ChangeTracker can be used to write logic that reacts to entities entering the DbContext or changing their state.

You can subscribe to these events from inside your DbContext constructor

ChangeTracker.Tracked += OnEntityTracked;
ChangeTracker.StateChanged += OnEntityStateChanged;

and do something like this:

void OnEntityTracked(object sender, EntityTrackedEventArgs e)
{
    if (!e.FromQuery && e.Entry.State == EntityState.Added && e.Entry.Entity is IHasCreationLastModified entity)
        entity.Created = DateTime.Now;
}

void OnEntityStateChanged(object sender, EntityStateChangedEventArgs e)
{
    if (e.NewState == EntityState.Modified && e.Entry.Entity is IHasCreationLastModified entity)
        entity.LastModified = DateTime.Now;
}