Sort a list from another list IDs

c# linq sorting collections
Borja López picture Borja López · Mar 7, 2013 · Viewed 60k times · Source

I have a list with some identifiers like this:

List<long> docIds = new List<long>() { 6, 1, 4, 7, 2 };

Morover, I have another list of <T> items, which are represented by the ids described above.

List<T> docs = GetDocsFromDb(...)

I need to keep the same order in both collections, so that the items in List<T> must be in the same position than in the first one (due to search engine scoring reasons). And this process cannot be done in the GetDocsFromDb() function.

If necessary, it's possible to change the second list into some other structure (Dictionary<long, T> for example), but I'd prefer not to change it.

Is there any simple and efficient way to do this "ordenation depending on some IDs" with LINQ?

Answer

Denys Denysenko picture Denys Denysenko · Mar 7, 2013 
docs = docs.OrderBy(d => docsIds.IndexOf(d.Id)).ToList();

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