vm = vm.OrderBy(item => item.Line).ToList();

vm 
 = 
 vm.
 OrderBy(item 
 => 
 item.
 Line).ThenByxxxxx.
 ToList();

//倒序
list.OrderByDescending(i => i.a).ThenByDescending(i => i.b);
//顺序
list.OrderBy(i => i.a).ThenBy(i => i.b);