LINQ - Get key-value pairs for dictionary with lists

Question

Let's say I have:

Dictionary<string, List<string>> test = new()
{
    { "animal", ["cat", "dog"] },
    { "fruit", ["banana", "apple"] }
};

I can use:

test.SelectMany(x => x.Value);

to get:

["cat", "dog", "banana", "apple"]

But is it possible to get:

[("animal", "cat"), ("animal", "dog"), ("fruit", "banana"), ("fruit", "apple")]

in a simple, readable way using LINQ dot syntax?

Answer 1

Use .SelectMany() to flatten the values from the list of tuples which combine from the key and each value.

var result = test.SelectMany(x => x.Value.Select(y => (x.Key, y)))
    .ToList();

Answer 2

You can use LINQ in the SelectMany itself to map the array value to the needed structure. For example with value tuples:

var valueTuples = test
    .SelectMany(x => x.Value.Select(val => (x.Key, val)))
    .ToList();

This will transform for each value in the array into pair of "current" key and value and flatten the resulting collection.