C#-引发异常的最佳方法

您是否知道以下引发异常的更好方法(更漂亮)？

public long GetPlaylistId(long songInPlaylistId)
{
    var songInPlaylist = service.GetById(songInPlaylistId);
    return songInPlaylist
            .With(x => x.Playlist)
            .ReturnValueOrException(x => x.Id, 
                                         new ArgumentException(
                                             "Bad argument 'songInPlaylistId'"));
}

单声道扩展方法：

public static TResult With<TInput, TResult>(this TInput obj, 
                                            Func<TInput, TResult> evaluator)
    where TInput : class
    where TResult : class
{
    return obj == null ? null : evaluator(obj);
}

public static TResult ReturnValueOrException<TInput, TResult>(
    this TInput obj, Func<TInput, TResult> evaluator, Exception exception)
    where TInput : class
{
    if (obj != null)
    {
        return evaluator(obj);
    }

    throw exception;
}

解决方法:

如果尝试获取没有播放列表的内容的播放列表是有效的,则您不应引发异常,而应返回一个表示“未找到”的特殊值(例如,0或-1取决于播放列表ID的工作方式).

或者,您可以编写一个TryGetPlaylistId()方法,该方法的工作方式类似于Microsoft的TryXXX()方法(例如SortedList.TryGetValue()),例如：

public bool TryGetPlaylistId(long songInPlaylistId, out long result)
{
    result = 0;
    var songInPlaylist = service.GetById(songInPlaylistId);

    if (songInPlaylist == null)
        return false;

    if (songInPlaylist.Playlist == null)
        return false;

    result = songInPlaylist.Playlist.Id;
    return true;
}

这种方法的一个小问题是,您在尝试诊断问题时会掩盖可能有用的信息.也许添加Debug.WriteLine()或其他某种形式的日志记录将很有用.关键是,您无法区分找不到播放列表ID的情况和找到但不包含播放列表的情况.

否则,您可能会抛出一个异常,该异常具有更多信息,例如：

public long GetPlaylistId(long songInPlaylistId)
{
    var songInPlaylist = service.GetById(songInPlaylistId);

    if (songInPlaylist == null)
        throw new InvalidOperationException("songInPlaylistId not found: " + songInPlaylistId);

    if (songInPlaylist.Playlist == null)
        throw new InvalidOperationException("Playlist for ID " + songInPlaylistId " has no playlist: ");

    return songInPlaylist.Playlist.Id;
}

在播放列表中找不到歌曲可能是有效的情况,但在没有播放列表的情况下找到歌曲是无效的,在这种情况下,您将在第一种情况下返回一个特殊值并引发异常在第二种情况下,例如：

public long GetPlaylistId(long songInPlaylistId)
{
    var songInPlaylist = service.GetById(songInPlaylistId);

    if (songInPlaylist == null)
        return -1; // -1 means "playlist not found".

    if (songInPlaylist.Playlist == null)
        throw new InvalidOperationException("Playlist for ID " + songInPlaylistId " has no playlist: ");

    return songInPlaylist.Playlist.Id;
}

无论如何,我个人认为您的扩展方法只是使代码模糊.

标签：monads,exception,null,c
来源： https://codeday.me/bug/20191121/2055097.html