public void ImportFromFileToTaskManager(string fileName, TaskManager taskManager) { if (String.IsNullOrEmpty(fileName)) { throw new ArgumentException("fileName can't be null or empty", "fileName"); } if (taskManager == null) { throw new ArgumentNullException("taskManager"); } var oldTasks = TaskStore.LoadFromFile <List <T> >(fileName); if (oldTasks == null) { string message = String.Format("Can't load old tasks from '{0}'", fileName); throw new InvalidOperationException(message); } ConvertTasks(oldTasks, taskManager); }