传一个参数，判断使用哪个排序：

List<A> lst = new List<A>
{
    new A { Id = "1", Name = "3", Age = 2 },
    new A { Id = "2", Name = "1", Age = 3 },
    new A { Id = "3", Name = "2", Age = 1 },
};
var switch_on = "idasc";
switch (switch_on)
{
    case "idasc":
        lst = lst.OrderBy(l => l.Id).ToList(); break;
    case "iddesc":
        lst = lst.OrderByDescending(l => l.Id).ToList(); break;
    case "ageasc":
        lst = lst.OrderBy(l => l.Age).ToList(); break;
    case "agedesc":
        lst = lst.OrderByDescending(l => l.Age).ToList(); break;
    default: break;
}