LINQ排序依据名称ThenBy ChildrenCollection.Name

问题描述

有没有LINQ没有办法做一个排序依据，然后使用父对象的孩子做二次订货做的ThenBy一个ThenBy？

<$ P $ 。p> _repository.GetActiveDepartmentGroupsWithDepartments（）排序依据（C => c.DepartmentGroupName）.ThenBy（C => c.Departments.OrderBy（D => d.DepartmentName））


在上述情况下，c.Departments是一个EntityCollection。

BTW：当我尝试了上面，然后在其上做了ToList（），我得到这个错误：

  DbSortClause表达式必须有一个类型是顺序相媲美。 
参数名：关键
  

在事先的任何帮助或指导谢谢

。

解决方案

好像你正在试图获得通过组，然后部门名称下令各部门的列表。如果是这样，那么你可能想要做这样的事情：

 在_repository.GetActiveDepartmentGroupsWithDepartments从C变种解析度=（）$ B从D $ b在c.Departments 
排序依据c.DepartmentGroupName，d.DepartmentName 
选择D组; 
  

或在方法的语法：

  VAR解析度= _repository.GetActiveDepartmentGroupsWithDepartments（）
 .SelectMany（C => c.Departments，（C，D）=>新建{C，D}）
 .OrderBy（X => xcDepartmentGroupName）
 .ThenBy（X => xdDepartmentName）
。选择（X => XD）; 
  

Is there any way in LINQ to do an OrderBy and then do a ThenBy with the ThenBy using the children of the parent object to do the secondary ordering?

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

In the above case, c.Departments is an EntityCollection.

BTW: When I try the above and then do a ToList() on it, I get this error:

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

Thanks in advance for any help or guidance.

解决方案

It seems like you're trying to get a list of all departments ordered by group then department name. If so, then you probably want to do something like this:

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

Or in method syntax:

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);

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