Sporangium.Expressions

static IEnumerable<Expression> GetSetProps<TSelf>(
  Expression self, Expression other, bool copy)
{
  PropertyInfo info = typeof(TSelf).GetProperty(nameof(Loaded));
  var iloaded = Expression.Property(self, info);
  var uloaded = Expression.Property(other, info);
  MethodInfo add = typeof(HashSet<string>).GetMethod(nameof(Add));

  foreach (info in GetValidProps(typeof(TSelf)))
  {
    var iprop = Expression.Property(self, info);
    var uprop = Expression.Property(other, info);
    var assign = Expression.Assign(iprop, uprop);
    var name = Expression.Constant(info.Name);
    var call = Expression.Call(iloaded, add, name);
    var block = Expression.Block(assign, call);
    var cond = MakeCond(iloaded, uloaded, name, copy);
    var ifthen = Expression.IfThen(cond, block);
    yield return ifthen;
  }
}

static Expression MakeCond(
  Expression iloaded, Expression uloaded, Expression name, bool copy)
{
  MethodInfo contains = typeof(HashSet<string>).GetMethod(nameof(Contains));
  var icall = Expression.Call(iloaded, contains, name);
  var ucall = Expression.Call(uloaded, contains, name);
  var lnot = Expression.Not(icall);
  var land = Expression.AndAlso(lnot, ucall);
  return copy ? land : ucall;
}