How to save a list to make it application persistent?

angelicaHoloLens

I have this codes to save and load my list

`
public void Save(List list)
{
BinaryFormatter bf = new BinaryFormatter();
FileStream file = File.Create(Application.persistentDataPath + "/objectlist.dat");

    ListData data = new ListData();
    data.objectList = list;

    bf.Serialize(file, data);
    file.Close();
}

/// <summary>
/// loads a serialized data, checks first if data exists
/// </summary>
public void Load()
{
    if (File.Exists(Application.persistentDataPath + "/objectlist.dat"))
    {
        BinaryFormatter bf = new BinaryFormatter();
        FileStream file = File.Open(Application.persistentDataPath + "/objectlist.data", FileMode.Open);
        ListData data = (ListData)bf.Deserialize(file);
        file.Close();

        objList = data.objectList;
    }
}

`

i also have
[Serializable] class ListData { public List<GameObject> objectList; }

When i simulate in unity, I have this error:
SerializationException: Type UnityEngine.GameObject is not marked as Serializable. IOException: Sharing violation on path C:\Users\DataMesh\AppData\LocalLow\DataMesh\EngineView\objectlist.dat

What am I doing wrong here?
This is the first time I do this and I can't really figure out.