'HashSet' does not contain a definition for 'ElementAt' в unity2d

юинити выдаёт следующую ошибку: Assets\scripts\SimpleRandomWalkDungeonGenerator.cs(35,46): error CS1061: 'HashSet<Vector2Int>' does not contain a definition for 'ElementAt' and no accessible extension method 'ElementAt' accepting a first argument of type 'HashSet<Vector2Int>' could be found (are you missing a using directive or an assembly reference?)

елси брать конкретную строчку к которой применима ошибка строчка 35 там код выглядит следующим образом: currentPosition = floorPositions.ElementAt(Random.Range(0, floorPositions.Count));
весь код выглядит следующим образом:

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using Random = UnityEngine.Random;
using UnityEngine.Tilemaps;

public class SimpleRandomWalkDungeonGenerator : MonoBehaviour
{
 [SerializeField]
 protected Vector2Int startPosition = Vector2Int.zero;

 public int iterations = 10;
 public int walkLength = 10;
 public bool startRandomlyEachIteration = true;

 [SerializeField]
 private TilemapVisualizer tilemapVisualizer;

 public void RunProceduralGeneration()
 {
 HashSet<Vector2Int> floorPositions = RunRandomWalk();
 tilemapVisualizer.PaintFloorTiles(floorPositions);
}

  protected HashSet<Vector2Int> RunRandomWalk()
 {
   var currentPosition = startPosition;
   HashSet<Vector2Int> floorPositions = new HashSet<Vector2Int>();
   for (int i = 0; i < iterations; i++)
  {
   var path = ProceduralGenerationAlgorithms.SimpleRandomWalk(currentPosition, walkLength);
   floorPositions.UnionWith(path);
   if (startRandomlyEachIteration)
   currentPosition = floorPositions.ElementAt(Random.Range(0, floorPositions.Count));
  }
   return floorPositions;
 }
}