How to get values into list from nested concurrent dictionary in c#

Question

I have a nested concurrent dictionary as given below:

ConcurrentDictionary<string,ConcurrentDictionary<string,<Class Object>>>

I want to get all objects (values of inner dictionary) into list for further processing without knowing any key.

I tried below two solutions but it does not work for me,

outer dictionary.Values.Select(x=> x.Values)
foreach loop

The problem with first solution is that it won't give only objects and second solution is time consuming.

Could you [edit] and show your `foreach` loop to see why it is time-consuming? — Sergey Kalinichenko, Jun 22 '17 at 14:02
Use `SelectMany` instead of just `Select`. https://stackoverflow.com/questions/958949/difference-between-select-and-selectmany — apocalypse, Jun 22 '17 at 14:08

score 1 · Answer 1 · answered Jun 22 '17 at 14:09

If you run dictionary.Values.Select(x=> x.Values) you would not get a list of object values from the inner dictionaries; you will get a list of lists of object values.

To "flatten" that list, use SelectMany:

foreach (var inner  in dictionary.Values.SelectMany(x=> x.Values)) {
    ...
}

How to get values into list from nested concurrent dictionary in c#

1 Answers1