Implementing a Base Class with Entity Framework

AuditableEntity.cs

namespace My.Models.BaseModels
{
    public class AuditableEntity
    {
        public int Id { get; set; }
        public DateTime CreatedDt { get; set; }
        public string CreatedBy { get; set; }
        public DateTime RevisedDt { get; set; }
        public string RevisedBy { get; set; }
    }
}

Claim.cs

namespace My.Models
{
    public class Claim : AuditableEntity
    {
        public ClaimType ClaimType { get; set; }
        public DateTime ClaimDate { get; set; }
    }
}

MyDbContext.cs

namespace My.DataAccess
{
    public class MyDbContext : DbContext
    {
        public MyDbContext() : base("database") // Web.config connection string
        {
        }

        public DbSet<Claim> Claims { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            // To get the Audit fields directly on the Table.
            modelBuilder.Entity<Claim>().Map(m => m.MapInheritedProperties()).ToTable("Claim");
        }
        
        public override int SaveChanges()
        {
            var entities = ChangeTracker.Entries().Where(x => x.Entity is AuditableEntity && (x.State == EntityState.Added || x.State == EntityState.Modified));

            var currentUsername = HttpContext.Current != null && HttpContext.Current.User != null
                ? HttpContext.Current.User.Identity.Name
                : "Anonymous";

            foreach (var entity in entities)
            {
                if (entity.State == EntityState.Added)
                {
                    ((AuditableEntity)entity.Entity).CreatedDt = DateTime.Now;
                    ((AuditableEntity)entity.Entity).CreatedBy = currentUsername;
                }

                ((AuditableEntity)entity.Entity).RevisedDt = DateTime.Now;
                ((AuditableEntity)entity.Entity).RevisedBy = currentUsername;
            }

            return base.SaveChanges();
        }
    }
}