Check out example codes for "c# list index". It will help you in understanding the concepts better.

Code Example 1

// add this to your namespace
public static IEnumerable<(T item, int index)> WithIndex<T>(this IEnumerable<T> source)
    return source.Select((item, index) => (item, index));

//do something like this

foreach (var (item, index) in collection.WithIndex())
    DoSomething(item, index);

Code Example 2

// Get the first item from the list

using System.Linq;

var myList = new List<string>{ "Yes", "No", "Maybe"};
var firstItem = myList.ElementAt(0);

// Do something with firstItem

Learn ReactJs, React Native from