LINQ OrderBy名称ThenBy ChildrenCollection.Name
有没有什么办法在LINQ做OrderBy，然后用ThenBy做一个ThenBy使用父对象的子对象进行二级排序？
_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：当我尝试上述，然后做一个ToList（），我得到这个错误：
DbSortClause expressions must have a type that is order comparable.
Parameter name: key
提前感谢您的帮助或指导。
看起来你正在试图获得所有按部门名称排序的部门清单。 如果是这样，那么你可能想要做这样的事情：
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);
由于Deparment是一个集合，因此您必须将其转换为标量才能将其用于排序。
一种选择是在集合中选择一个实体，例如第一个部门的名称：
_repository.GetActiveDepartmentGroupsWithDepartments()
.OrderBy(c => c.DepartmentGroupName)
.ThenBy(c => c.Departments
.OrderBy(d => d.DepartmentName)
.FirstOrDefault()
.DepartmentName
)
另一种选择是通过集合本身的属性来订购，例如部门的数量：
_repository.GetActiveDepartmentGroupsWithDepartments()
.OrderBy(c => c.DepartmentGroupName)
.ThenBy(c => c.Departments.Count())