How can I convert a string[] into a dictionary<int, string> using a separate int[] as the key set?

Question

I know that Linq offers the ToDictionary(key, value) method, and I'm sure there's a way to be able to do what I'm trying to achieve but I can't quite figure it out.

I have two arrays, the first being conditionalIds, which is simply an int[] that stores a number of Ids, the second array is a string[] called conditionalAnswers. I essentially want to combine and map these two arrays so that each of the Ids stores in conditionalIds maps to the correct answer.

var conditionalIds = _currentRuleSet.MultiConditionalQuestionIds;
var conditionalAnswers = _currentRuleSet.MultiConditionalQuestionAnswers;
var map = conditionalAnswers.ToDictionary(conditionalIds, x => x[]);

However I'm not sure how to structure the Linq query to achieve this.

why linq? do both lists have the same number of values?

BugFinder
– BugFinder

2019-05-20 08:45:43 +00:00
Commented May 20, 2019 at 8:45 — BugFinder
– BugFinder, Commented May 20, 2019 at 8:45
How do you know what is the correct answer of a given id?

Oram
– Oram

2019-05-20 08:53:35 +00:00
Commented May 20, 2019 at 8:53 — Oram
– Oram, Commented May 20, 2019 at 8:53

DavidG · Accepted Answer · 2019-05-20 08:56:56Z

3

Assuming both lists have the same number of items and they are in the correct order, you want to use Linq Enumerable.Zip, for example this will give you an IEnumerable of an anonymous type:

var map = conditionalIds.Zip(
    conditionalAnswers, 
    (id, answer) => new { id, answer });

And if you really want a dictionary:

var dictionary = map.ToDictionary(x => x.id, x => x.answer);

edited May 20, 2019 at 8:56

answered May 20, 2019 at 8:51

DavidG

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DS Passionate · Accepted Answer · 2019-05-20 09:19:17Z

1

Ans given by @SeM is correct, but one thing is that question id array should have unique values.

    int[] queId={6,4,9,2,10};
string[] answers ={"Ans1", "Ans3","Ans4","Ans16","Ans18"} ;
Dictionary<int, string> queAnsBank=answers.select((value,index)=>new{Key=queId[index],Value=value}).ToDictionary(i=>i.Key,i=>i.Value);

You can also achieve this by for loop.

answered May 20, 2019 at 9:19

DS Passionate

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Comments

Renat · Accepted Answer · 2019-05-20 08:50:27Z

0

It looks like target dictionary could be constructed as:

        Dictionary<int, string> map = conditionalIds.ToDictionary(
            keySelector: id => id,
            elementSelector: id => conditionalAnswers[id]);

answered May 20, 2019 at 8:50

Renat

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Comments

SᴇM · Accepted Answer · 2019-05-20 08:53:34Z

0

If you are trying to map based on conditionalAnswers and conditionalIds indices, you can do something like this:

var map = conditionalAnswers
          .Select((s, i) => new { Key = conditionalIds[i], Value = s })
          .ToDictionary(d => d.Key, d => d.Value);

References: Enumerable.Select Method

answered May 20, 2019 at 8:53

SᴇM

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