Unity : Can i see an example of [ExecuteInEditMode] and [SelectionBase] ?

CubeEditor.cs

[ExecuteInEditMode]
[SelectionBase]
public class CubeEditor : MonoBehaviour
{
    
    [SerializeField][Range(1f, 20f)] float gridSize = 10f;

    TextMesh textMesh;

    private void Start()
    {
        textMesh = GetComponentInChildren<TextMesh>();
        textMesh.text = "BIP3";
    }
    void Update()
    {
        //Debug.Log("Editor causes this update");
        Vector3 snapPos;
        snapPos.x = Mathf.RoundToInt(transform.position.x / gridSize) * gridSize;
        snapPos.z = Mathf.RoundToInt(transform.position.z / gridSize) * gridSize;
        transform.position = new Vector3(snapPos.x, 0f, snapPos.z);
        string labelText = snapPos.x / gridSize + "," + snapPos.z / gridSize;
        textMesh.text = labelText;
        gameObject.name = labelText;
    }
}