Unity-Technologies/UnityCsReference · error · ArgumentException

gameObjects array is empty

Error message

gameObjects array is empty

What it means

Thrown by AddGameObjectsToPrefabAndConnect when the `gameObjects` array is non-null but has zero elements. Connecting nothing is meaningless, so Unity rejects it as ArgumentException before touching the target prefab.

Source

Thrown at Editor/Mono/Prefabs/PrefabUtility.bindings.cs:277

        [StaticAccessor("PrefabUtilityBindings", StaticAccessorType.DoubleColon)]
        [NativeMethod(ThrowsException = true)]
        extern private static GameObject SaveAsPrefabAsset_Internal([NotNull] GameObject root, string path, out bool success);

        [StaticAccessor("PrefabUtilityBindings", StaticAccessorType.DoubleColon)]
        [NativeMethod(ThrowsException = true)]
        extern private static GameObject SaveAsPrefabAssetAndConnect_Internal([NotNull] GameObject root, string path, out bool success);

        [StaticAccessor("PrefabUtilityBindings", StaticAccessorType.DoubleColon)]
        [NativeMethod(ThrowsException = true)]
        extern private static GameObject SavePrefabAsset_Internal([NotNull] GameObject root, out bool success);

        internal static void AddGameObjectsToPrefabAndConnect(GameObject[] gameObjects, Object targetPrefab)
        {
            if (gameObjects == null)
                throw new ArgumentNullException("gameObjects");

            if (gameObjects.Length == 0)
                throw new ArgumentException("gameObjects array is empty");

            if (targetPrefab == null)
                throw new ArgumentNullException("targetPrefab");

            if (!PrefabUtility.IsPartOfPrefabAsset(targetPrefab))
                throw new ArgumentException("Target Prefab has to be a Prefab Asset");

            Object targetPrefabInstance = null;

            var targetPrefabObject = PrefabUtility.GetPrefabAssetHandle(targetPrefab);

            foreach (GameObject go in gameObjects)
            {
                if (go == null)
                    throw new ArgumentException("GameObject in input 'gameObjects' array is null");

                if (EditorUtility.IsPersistent(go))  // Prefab asset
                    throw new ArgumentException("Game object is part of a prefab");

View on GitHub (pinned to 225b0fbdb5)

Solutions

1. Check Length > 0 before calling and early-return or warn the user.
2. Filter/guarantee at least one valid GameObject upstream.
3. Disable the menu item / button when the selection is empty.

Example fix

// before
var gos = Selection.gameObjects.Where(g => g.CompareTag("Enemy")).ToArray();
PrefabUtility.AddGameObjectsToPrefabAndConnect(gos, target); // may be empty

// after
var gos = Selection.gameObjects.Where(g => g.CompareTag("Enemy")).ToArray();
if (gos.Length == 0) { Debug.LogWarning("No Enemy selected."); return; }
PrefabUtility.AddGameObjectsToPrefabAndConnect(gos, target);

if (gameObjects == null || gameObjects.Length == 0)
{ Debug.LogWarning("No GameObjects to connect."); return; }

When it happens

Trigger: Calling with new GameObject[0], Array.Empty<GameObject>(), or a filtered/selected list that resolved to no elements.

Common situations: Selection-based tools when the user invoked the action with nothing selected. LINQ Where clauses filtering out everything. Loops that never Add to a list.

Related errors

• gameObjects
• targetPrefab
• Target Prefab has to be a Prefab Asset
• GameObject in input 'gameObjects' array is null
• Game object is part of a prefab

AI-assisted analysis of Unity-Technologies/UnityCsReference@225b0fbdb5 (2026-08-13). Data as JSON: /api/errors/8e229d8ea06b9b5d. Report an issue: GitHub.