Unable to validate entity using Entity Framework Core (.net core)

I am using EntityFramework Core to connect to database in .Net core web API. I am facing issue while trying validate the entity before submit changes to DB i.e Context.SaveChanges(). Validation error is not thrown even though entity is not meeting specific condition. If i add the condition using attribute it work, but it is not working when conditions are added using Model build.

Is there way to properly validate entity which are created using Model builder?

Entity:

public class AppSession
{
    public AppSession()
    {

    }

    public long AppSessionId { get; set; }
    public Guid ExternalAppSessionId { get; set; }
    public DateTime CreatedDate { get; set; }
    public Sources SourceId { get; set; }
    public string Gcid { get; set; }
    //[StringLength(60)]
    public string UserAgent { get; set; }
    public string SessionReferrer { get; set; }      

}

Model Builder:

public class AppSessionConfig : IEntityTypeConfiguration<AppSession>
    {
        public void Configure(EntityTypeBuilder<AppSession> builder)
        {
            builder.Property(e => e.AppSessionId).HasColumnName("AppSessionID");

            builder.Property(e => e.ExternalAppSessionId).HasColumnName("ExternalAppSessionID");

            builder.Property(e => e.Gcid)
                 .HasColumnName("GCID")
                 .HasMaxLength(200)
                 .IsUnicode(false);


            builder.Property(e => e.Keyword)
                 .HasMaxLength(255)
                 .IsUnicode(false);

            builder.Property(e => e.SessionReferrer)
                 .HasMaxLength(512)
                 .IsUnicode(false);

            builder.Property(e => e.SourceId).HasColumnName("SourceID");

            builder.Property(e => e.UserAgent)
                 .HasMaxLength(50)
                 .IsUnicode(false);

        }

Context:

public partial class TestDbContext : DbContext,IDbContext
{
    public TestDbContext(DbContextOptions<TestDbContext> options)
   : base(options)
    { }

    public virtual DbSet<Entities.AppSession> AppSessions { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.ApplyConfiguration(new AppSessionConfig());
   }

    public override int SaveChanges()
    {
        ValidateEntities();
        return base.SaveChanges();
    }

private void ValidateEntities()
    {
        var entities = (from entry in ChangeTracker.Entries()
                        where entry.State == EntityState.Modified || entry.State == EntityState.Added
                        select entry.Entity);

        var validationResults = new List<ValidationResult>();
        foreach (var entity in entities)
        {
            var validationContext = new ValidationContext(entity);
            Validator.ValidateObject(entity, validationContext, true);
        }
    }

}

Thanks,

Upvotes: 2