LINQ OrderBy Name ThenBy ChildrenCollection.Name

Question

在LINQ中有没有办法做一个OrderBy,然后用ThenBy做一个ThenBy,使用父对象的子进行二次排序？

_repository.GetActiveDepartmentGroupsWithDepartments().OrderBy(c => c.DepartmentGroupName).ThenBy(c => c.Departments.OrderBy(d => d.DepartmentName))

在上面的例子中,c.Departments是一个EntityCollection.

顺便说一句:当我尝试上面的内容然后对其执行ToList()时,我收到此错误:

DbSortClause expressions must have a type that is order comparable.
Parameter name: key

在此先感谢任何帮助或指导.

Answer 1

您似乎正在尝试获取按组和部门名称排序的所有部门的列表.如果是这样,那么你可能想做这样的事情:

var res = from c in _repository.GetActiveDepartmentGroupsWithDepartments()
          from d in c.Departments
          orderby c.DepartmentGroupName, d.DepartmentName
          select d;

或者在方法语法中:

var res = _repository.GetActiveDepartmentGroupsWithDepartments()
                     .SelectMany(c => c.Departments, (c,d) => new { c, d })
                     .OrderBy(x => x.c.DepartmentGroupName)
                     .ThenBy(x => x.d.DepartmentName)
                     .Select(x => x.d);