Backingfield is null in EF Core 3.1 , Lazy loading enabled

Question

I am using Lazy Loading in EF core 3.1 and when i try to get the navigation data,it doesn't load.

public class Template
{
    private readonly List<Spec>               _specs;
    public virtual   IReadOnlyList<Spec> Specs   => _specs;

  public Template()
{
   _specs=new List<Spec>();
}


public void Add (Spec spec)
{
    var specs=_specs.Contains(spec); // _specs list will be 0
    ...
}

}