How to use the IEqualityComparer

I have some bells in my database with the same number. I want to get all of them without duplication. I created a compare class to do this work, but the execution of the function causes a big delay from the function without distinct, from 0.6 sec to 3.2 sec!

Am I doing it right or do I have to use another method?

reg.AddRange(
    (from a in this.dataContext.reglements
     join b in this.dataContext.Clients on a.Id_client equals b.Id
     where a.date_v <= datefin && a.date_v >= datedeb
     where a.Id_client == b.Id
     orderby a.date_v descending 
     select new Class_reglement
     {
         nom  = b.Nom,
         code = b.code,
         Numf = a.Numf,
     })
    .AsEnumerable()
    .Distinct(new Compare())
    .ToList());

class Compare : IEqualityComparer<Class_reglement>
{
    public bool Equals(Class_reglement x, Class_reglement y)
    {
        if (x.Numf == y.Numf)
        {
            return true;
        }
        else { return false; }
    }
    public int GetHashCode(Class_reglement codeh)
    {
        return 0;
    }
}