DataContractSerializer序列化解决办法

DataContractSerializer序列化
    public static bool WriteObjectToFile(string path, Type type, object obj)
        {
            try
            {
                FileStream stream = CreateFile(path);
                new DataContractSerializer(type).WriteObject(stream, obj);
                stream.Close();
                return true;
            }
            catch (Exception)
            {
                return false;
            }
        }

为什么当 obj对象有BitmapImage就引发异常，怎么样才能使对象即使有BitmapImage也不会引发异常
[解决办法]