c# - Use a foreach loop within a foreach loop in a linq query

Question

I am wondering on how to do the following. I have the Linq query:

Items items.Where(i => i.GetType() == typeof(SubItem))
                .Cast<SubItem>()
                .ToList()
                .ForEach(i => i.SomeList.Add(i.SomeObject.ForEach(i => i.SomeString)));

My question is about i.SomeList.Add(). I want to return a couple of string values to i.SomeList.Add() from i.SomeObject but I do not know how I can do this in this way? Is it even possible like this to have another ForEach Loop within a Linq ForEach usinq Linq query?

question from:https://stackoverflow.com/questions/65852140/use-a-foreach-loop-within-a-foreach-loop-in-a-linq-query

Answer 1

I believe this foreach loop will achieve your goal, if I've understood the problem.

It will loop over any element of items that is a (or is derived from) SubItem. It will then select all SomeObject.SomeString strings and add them to the SomeList.

foreach (var subItem in items.OfType<SubItem>()) {
    subItem.SomeList.AddRange(subItem.SomeObject.Select(o => o.SomeString));
}

This is a compilation of suggestions from Panagiotis Kanavos, juharr, and Aluan Haddad.