public static DbQuery<DbSelectExpression> Having(this DbQuery<DbSelectExpression> dbSelectQuery, Func<DbExpressionFactory, DbExpression> expressionSelector)
{
var dbExpression = expressionSelector(DbExpressionFactory);
if (!dbSelectQuery.QueryExpression.HavingExpression.IsNull())
dbExpression = DbExpressionFactory.List(new[] { dbSelectQuery.QueryExpression.FromExpression, dbExpression });
dbSelectQuery.QueryExpression.HavingExpression = dbExpression;
return dbSelectQuery;
}