FindLastBy · Software Engineering Wiki

Returns the last element in a collection that matches the given predicate function, match.

Use IEnumerable.Where() to filter out all values in data for which match returns false.
Use IEnumerable.Last() to return only the last matching element.

using System.Collections.Generic;
using System.Linq;

public static partial class _30s 
{
  public static T FindLastBy<T>(IEnumerable<T> data, Predicate<T> match)
  {
    return data.Where(i => match(i)).Last();
  }
}

int[] nums = {1, 2, 4, 5, 2, 2, 4};

_30s.FindLastBy(nums, x => x % 2 == 0); // 4