Error when Building Project: Error building Player because scripts have compile errors in the editor

You cannot build any your script that contains using UnityEditor; or class/API from the UnityEditor namespace. This is why you should put any script that contains any of these in a folder called Editor.

When Unity is building your project, it ignores any script placed in this folder since it considers them as an Editor script or plugin.

You have three choices:

  1. Remove using UnityEditor; from your script.
  2. Place your script in a folder called Editor.
  3. Use Unity’s preprocessor directive to determie when not to compile with using UnityEditor; You can do that by replacing: using UnityEditor; with #if UNITY_EDITOR using UnityEditor; #endif

I would go with #2. Create a different script for any Editor stuff and place it in the Editor folder. Note that Unity will not compile any script in this folder when building your project. Scripts in this folder are meant to run in the Editor only.