private static void AppendCharacteristicIn(this IFacetsBuilder <Entities.Product> facetsBuilder,
                                                   ICollection <string> values)
        {
            facetsBuilder.AppendText(" and $char/value = (");
            int count     = 0;
            int lastIndex = values.Count - 1;

            foreach (string value in values)
            {
                string paramName = facetsBuilder.GetParamName();
                facetsBuilder.AppendText("sql:variable(\"");
                facetsBuilder.AppendText(paramName);
                facetsBuilder.AppendText("\")");
                facetsBuilder.AddParameter(paramName, value);

                if (count >= lastIndex)
                {
                    break;
                }

                facetsBuilder.AppendText(",");
                count++;
            }

            facetsBuilder.AppendText(")");
        }
        private static void AppendCharacteristicName(this IFacetsBuilder <Entities.Product> facetsBuilder, string name)
        {
            string paramName = facetsBuilder.GetParamName();

            facetsBuilder.AppendText("$char/name = sql:variable(\"");
            facetsBuilder.AppendText(paramName);
            facetsBuilder.AppendText("\")");
            facetsBuilder.AddParameter(paramName, name);
        }