How to hydrate a Dictionary with the results of async calls?

Question

Suppose I have code that looks like this:

public async Task DoSomethingReturnString(int n) { ... }
int[] numbers = new int[] { 1, 2 , 3};
         


        

Answer 1

If you insist on doing it with linq, Task.WhenAll is the key to "hydrate" the dictionary:

int[] numbers = new int[] { 1, 2 , 3};

KeyValuePair[] keyValArray = //using KeyValuePair<,> to avoid GC pressure
    await Task.WhenAll(numbers.Select(async p => 
        new KeyValuePair(p, await DoSomethingReturnString(p))));

Dictionary dict = keyValArray.ToDictionary(p => p.Key, p => p.Value);