bool ApplyAll()
        {
            // Collect Prefab Asset paths and also check if there's more than one of the same.
            HashSet <string> prefabAssetPaths = new HashSet <string>();
            bool             multipleOfSame   = false;

            for (int i = 0; i < m_SelectedGameObjects.Length; i++)
            {
                string prefabAssetPath = PrefabUtility.GetPrefabAssetPathOfNearestInstanceRoot(m_SelectedGameObjects[i]);
                if (prefabAssetPaths.Contains(prefabAssetPath))
                {
                    multipleOfSame = true;
                }
                else
                {
                    prefabAssetPaths.Add(prefabAssetPath);
                }
            }

            // If more than one instance of the same Prefab Asset, show dialog to user.
            if (multipleOfSame && !EditorUtility.DisplayDialog(
                    L10n.Tr("Multiple instances of same Prefab Asset"),
                    L10n.Tr("Multiple instances of the same Prefab Asset were detected. Potentially conflicting overrides will be applied sequentially and will overwrite each other."),
                    L10n.Tr("OK"),
                    L10n.Tr("Cancel")))
            {
                return(false);
            }

            // Make sure assets are checked out in version control.
            if (!PrefabUtility.PromptAndCheckoutPrefabIfNeeded(prefabAssetPaths.ToArray(), PrefabUtility.SaveVerb.Apply))
            {
                return(false);
            }

            var undoStructs = new List <ApplyAllUndo>();
            var actionName  = "ApplyAll";

            for (var i = 0; i < m_SelectedGameObjects.Length; i++)
            {
                var us = new ApplyAllUndo();
                us.correspondingSourceObject = (GameObject)PrefabUtility.GetCorrespondingObjectFromSource(m_SelectedGameObjects[i]);
                Undo.RegisterFullObjectHierarchyUndo(us.correspondingSourceObject, actionName); // handles changes to existing objects and object what will be deleted but not objects that are created
                GameObject prefabInstanceRoot = PrefabUtility.GetOutermostPrefabInstanceRoot(m_SelectedGameObjects[i]);
                Undo.RegisterFullObjectHierarchyUndo(prefabInstanceRoot, actionName);

                us.prefabHierarchy = new HashSet <int>();
                PrefabUtility.GetObjectListFromHierarchy(us.prefabHierarchy, us.correspondingSourceObject);
                undoStructs.Add(us);
            }

            // Apply sequentially.
            AssetDatabase.StartAssetEditing();
            try
            {
                foreach (var t in m_SelectedGameObjects)
                {
                    PrefabUtility.ApplyPrefabInstance(t, InteractionMode.UserAction);
                }
            }
            finally
            {
                AssetDatabase.StopAssetEditing();
            }

            foreach (var t in undoStructs)
            {
                var danglingObjects = new List <Object>();
                PrefabUtility.CollectAddedObjects(t.correspondingSourceObject, t.prefabHierarchy, danglingObjects);
                foreach (var component in danglingObjects)
                {
                    Undo.RegisterCreatedObjectUndoToFrontOfUndoQueue(component, actionName);
                }
            }

            EditorUtility.ForceRebuildInspectors();
            return(true);
        }