Question

If I have a IDictionary<int, int>, is it possible to receive a IEnumerable<int>, which
would contain every KeyValuePair<int, int> disassembled into two (int, int) entries inserted one after another?

Small example:

Dictionary:
5 - 25
6 - 36
7 - 49

Wanted Enumerable:
5, 25, 6, 36, 7, 49

Also, I wanted to have this in one super-pretty statement, but I couldn’t think of an appropriate one 🙂

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Update:

Does LINQ allow to insert more than one element per .Select statement, something sharing the idea of:

xyz.Select(t => (t, null))

so that the resulting Enumerable would contain both t and null right after it?

Answer 1

You could use SelectMany<TSource, TResult>(IEnumerable<TSource>, Func<TSource, IEnumerable<TResult>>) (plus overloads). Here’s an example

var dict = new Dictionary<int, int> {
   { 5, 25 },
   { 6, 36 },
   { 7, 49 } 
}; 

var projection = dict.SelectMany(kv => new[] { kv.Key, kv.Value });

As per the comments, this is just one way of achieving what you have asked.