EF Core 2.1 [change tracking] - saving all related entities

Maybe the title is misunderstood but I'm gonna try to explain my situation here.

So, considering my entity Person that has a virtual property Country, as follow:

public class Person {
    public long Id { get; set;}
    public short IdCountry { get; set;}
    public virtual Country Country { get; set; }
    ...
}

and the mapping as follow:

...
builder.HasOne(c => c.Country)
    .WithMany()
    .HasForeignKey(c => c.IdCountry);

and my repository is generic.

What happens here is, when I try to save some change in Person, the Country entity state came to me as Added wich does not make sense.

I'm exposing here a similar example that what is happening to me. Actually, I have like five others virtual properties in my class Person and some of them are in this state (Added).

Has anyone ever dealt with it before? Thanks in advance.

EDIT: Ansewing @alans reply: I'm doing something similar as follow:

foreach (var entrie in entry.Context.ChangeTracker.Entries())
{
    try
    {
        key = entrie.Entity.GetType().GetProperty("Id").GetValue(entrie.Entity, null);
    }
    catch (Exception ex)
    {
        key = null;
    }
    if (key != null && entrie.State == EntityState.Added)
    {
        entrie.State = EntityState.Unchanged;
    }
    else if (Convert.ChangeType(key, typeof(long)) as long? == 0)
    {
        entrie.State = EntityState.Added;
    }
}
_dbContext.SaveChanges();

@TanvirArjel this method above is where the state come as Added