[英]Ordering Linq list by array elements
I have below code -我有以下代码 -
var refNosToOrder = new int[9] {1,2,3,4,5,6,7,8,9}
var orderedList = lst.OrderBy(x=>x.RefNo==7)
.ThenBy(y=> refNosToOrder.Contains(y.RefNo)).ToList();
lst
is list of class object containing int property - RefNo: ie List<SampleClass>
lst
是包含 int 属性的 class object 的列表 - RefNo: ie List<SampleClass>
class SampleClass
{
public int RefNo {get;set;}
}
lst
contains all the unsorted data of RefNo
: lst
包含RefNo
的所有未排序数据:
lst = 2,4,6,9,7,5,8,1,3
What I want to do -我想做的事 -
First I want to order lst
by keeping first element as - 7
;首先,我想通过将第一个元素保留为 -
7
来订购lst
; then for the rest of the list, it should be ordered as the array refNosToOrder
那么对于列表的 rest,它应该被排序为数组
refNosToOrder
ie Final output I am expecting to be -即最终 output 我期望是 -
7,1,2,3,4,5,6,8,9
With the above code -使用上面的代码 -
var orderedList = lst.OrderBy(x=>x.RefNo==7)
.ThenBy(y=> refNosToOrder.Contains(y.RefNo)).ToList();
It is giving - 2,4,6,9,7,5,8,1,3
ie this code is not at all ordering the list.它给出了 -
2,4,6,9,7,5,8,1,3
,即这个代码根本没有对列表进行排序。
Contains
returns a boolean of whether an element is in a list or not, which won't be very helpful here. Contains
返回一个元素是否在列表中的 boolean,这在这里不会很有帮助。 Instead, you could sort by the index of that element:相反,您可以按该元素的索引进行排序:
var orderedList =
lst.OrderBy(x => x.RefNo != 7)
.ThenBy(y => Array.IndexOf(refNosToOrder, y.RefNo))
.ToList();
EDIT:编辑:
Following up on Jeroen Mostert's comment, this sorting has quadratic complexity.继 Jeroen Mostert 的评论之后,这种排序具有二次复杂性。 For large
refNosToOrder
it may be more efficient to first convert the array to a dictionary of orders and then use it for the sorting:对于较大
refNosToOrder
,首先将数组转换为订单字典然后将其用于排序可能更有效:
var orderDict =
Enumerable.Range(0, refNosToOrder.Length).ToDictionary(i => refNosToOrder[i]);
var orderedList =
lst.OrderBy(x => x.RefNo != 7).ThenBy(y => orderDict[y.RefNo]).ToList();
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