ソースコード

#if UNITY_EDITOR

using UnityEditor;
using UnityEngine;
using UnityEngine.UI;

public sealed class Example : MonoBehaviour
{
    [SerializeField] private GameObject m_prefab;
    [SerializeField] private RawImage   m_rawImage;

    private void Awake()
    {
        m_rawImage.texture = 
            AssetPreview.GetAssetPreview( m_prefab );
    }
}

#endif