Question

Using a LINQ query (with C#) how would I go about do something like this (pseudocode)?

I’d look to do something like this is in places where, for example, I might generate 1000’s of lists of 100’s of random (bounded) integers, where I want to track the smallest of them as they’re generated.

Best <- null value 

Foreach N in Iterations
    NewList <- List of 100 randomly generated numbers
    If Best is null
        Best <- NewList

    If Sum(NewList) < Sum(Best)
        Best <- NewList

Select Best

I’ve tried all sorts of things, but I can’t really get it working. This isn’t for any kind of project or work, just for my own curiosity!

Example of what I was thinking:

let R = new Random()   
let Best = Enumerable.Range(0, 100).Select(S => R.Next(-100, 100)).ToArray()

//Where this from clause is acting like a for loop 
from N in Iterations 
    let NewList = Enumerable.Range(0, 100).Select(S => R.Next(-100, 100))
    Best = (NewList.Sum() < Best.Sum())? NewList : Best;

select Best

Answer 1

I believe you are looking for fold (aka “reduce”) which is known as Aggregate in LINQ.

(IEnumerable.Min/Max are special-cases, but can be written in terms of fold/Aggregate.)

int Max (IEnumerable<int> x) {
  return x.Aggregate(int.MinValue, (prev, cur) => prev > cur ? prev : cur);
}
Max(new int[] { 1, 42, 2, 3 }); // 42

Happy coding.