How to sort an IList with basis of another sorted list in C#?

Question

I have two ILists (of different Types), a and b. They are the same size because every a.G.Id matches exactly one b.G.Id.

b is sorted (because of an OrderBy(b=>b.SortVal). Now I want to sort the list a. (Classical sorting algorithms would help if I would have an a.SortVal and would just sort a without the help of a second list but that's not the case).

An alternative to do that in the C#-Code could be a stored procedure (SQL). But I should write a new question for that — thestruggleisreal, Jan 23 '19 at 14:07
"I didn't find a duplicate for this case !" Did you try anything beyond searching for an exact duplicate? What are your own attepns so far? — MakePeaceGreatAgain, Jan 23 '19 at 14:09

vc 74 · Answer 1 · 2019-01-23T14:17:51.707

1

var dic = a.ToDictionary(x => x.gId);

var aSorted = b.Select(x => dic[x.G.Id];

should do it

Basically creating a dictionary to identify a's items by their gId and then using it while looping through b's (sorted) items should return the items in a as ordered in b.

The dictionary is used to make lookups faster than a scan.

edited Jan 23 '19 at 14:17

answered Jan 23 '19 at 14:08

vc 74

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score 0 · Answer 2 · answered Jan 23 '19 at 14:08

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You can do something like this:

a = a.OrderBy(x => b.FindIndex(b.G.Id == x.gId));

I've answered a question much like this one before - Sort a list by a custom order - but it's not an exact duplicate.

answered Jan 23 '19 at 14:08

Zohar Peled

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thestruggleisreal · Accepted Answer · 2019-01-23T15:12:40.380

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I did .Include(x=>x.G) when initialising b. Then I defined and initialised a new list bIds=b.Select(b=>b.G.Id).ToList();

and

a = a.OrderBy(x => bIds.IndexOf(x.G.Id)).ToList();

did it.

(with the help of https://stackoverflow.com/a/15275394/10357604 )

edited Jan 23 '19 at 15:12

answered Jan 23 '19 at 15:06

thestruggleisreal

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How to sort an IList with basis of another sorted list in C#?

3 Answers3