// create interface IAuditableModel
public interface IAuditableModel
{
    DateTime CreationTime { get; set; }
    DateTime? ModifiedDate { get; set; }
}

// override two method in DbContext 
public override int SaveChanges()
        {
            DateTimeChange();

            return base.SaveChanges();
        }

        public override Task<int> SaveChangesAsync(bool acceptAllChangesOnSuccess, CancellationToken cancellationToken = default(CancellationToken))
        {
            DateTimeChange();

            return base.SaveChangesAsync(acceptAllChangesOnSuccess, cancellationToken);
        }

        private void DateTimeChange()
        {
            var added = ChangeTracker.Entries<IAuditableModel>().Where(E => E.State == EntityState.Added).ToList();

            added.ForEach(E =>
            {
                E.Property(x => x.CreationTime).CurrentValue = DateTime.UtcNow;
                E.Property(x => x.CreationTime).IsModified = true;
            });

            var modified = ChangeTracker.Entries<IAuditableModel>().Where(E => E.State == EntityState.Modified).ToList();

            modified.ForEach(E =>
            {
                E.Property(x => x.ModifiedDate).CurrentValue = DateTime.UtcNow;
                E.Property(x => x.ModifiedDate).IsModified = true;

                E.Property(x => x.CreationTime).CurrentValue = E.Property(x => x.CreationTime).OriginalValue;
                E.Property(x => x.CreationTime).IsModified = false;
            });
        }