public string Query(string filter, FilterGroup fg)
{
FilterGroup filterGroup = ConvertToObject <FilterGroup>(filter ?? "");
string whereSql = FilterTranslator.ToSql(filterGroup);
Expression <Func <Student, bool> > whereLambda = FilterTranslator.ToLambdaExpression <Student>(filterGroup ?? fg);
return(ToJson(new { rows = MockStudents().Where(whereLambda), total = 1 }));
}