protected override Expression VisitUnary(UnaryExpression u) {
throw new NotSupportedException(
string.Format(
"Unrn opertor '{0}' nen podporovn.",
u.NodeType));
}

protected override Expression VisitConstant(ConstantExpression c) {
if (c.Value is IQueryable) {
// Pedpokld, e konstantn uzly s rozhranm IQueryable
// jsou sekvence let.
return c;
}
throw new NotSupportedException(
string.Format(
"Konstanta pro '{0}' nen podporovna.",
c.ToString()));
}

protected override Expression VisitMemberAccess(MemberExpression m) {
throw new NotSupportedException(
string.Format(
"len '{0}' nen podporovn.",
m.Member.Name));
}
