error CS0103: The name 'AssetPreview' does not exist in the current context

Question

In my Unity Project I've C# code to get Prefabs preview image in png format.

In Unity Play mode I have not errors with this Script and everything it's ok, but when I trie to build my project I've receive error.

I spend a lot of times to try understand where I'd made a mistake, but no result.

Can some body help with this problem?

C# Script

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using System.IO;
using System;

public class LoadTexture : MonoBehaviour
{
    [System.Serializable]
    public class LoadTex
    {
        public string name;
        public GameObject texture;
        public Texture2D gameObjectTex;
        public Texture gameObjTex;
    }

    public List<LoadTex> ItemTablezz = new List<LoadTex>();

    // Start is called before the first frame update
    void Start()
    {
        for (int i = 0; i < ItemTablezz.Count; i++)
        {
            var getImage = UnityEditor.AssetPreview.GetAssetPreview(ItemTablezz[i].texture);
            print(getImage);

            ItemTablezz[i].gameObjectTex = getImage;
        }
    }

    // Update is called once per frame
    void Update()
    {
        CheckIfNull();
    }

    void CheckIfNull()
    {
        for (int k = 0; k < ItemTablezz.Count; k++)
        {
            Texture2D tex = new Texture2D(128, 128, TextureFormat.RGBA32, false);
            Color[] colors = ItemTablezz[k].gameObjectTex.GetPixels();
            int i = 0;
            Color alpha = colors[i];
            for (; i < colors.Length; i++)
            {
                if (colors[i] == alpha)
                {
                    colors[i].a = 0;
                }
            }

            tex.SetPixels(colors);
            tex.Apply();
            byte[] png = tex.EncodeToPNG();
            File.WriteAllBytes(Application.persistentDataPath + "/" + ItemTablezz[k].name + ".png", png);
        }
    }
}

error CS0103: The name 'AssetPreview' does not exist in the current context

Where I'd made mistake?