我的 .saveChanges() 方法没有保存，因为它表示非静态字段、方法或属性需要对象引用

Question

调用 .SaveChanges() 时出现错误。它告诉我非静态字段、方法或属性“SongDatabase.Songs”需要对象引用。这是我的控制器代码。有人能告诉我为什么会发生这个错误吗？

[HttpPost]
    public ActionResult Add(Song song)
    {
        using (SongDatabase db = new SongDatabase())
        {
            SongDatabase.Songs.Add(song);
            SongDatabase.SaveChanges();
        }

        return RedirectToAction("Music");
    }

这是我的歌曲数据库代码。

public class SongDatabase : DbContext
{
    public DbSet<Song> Songs { get; set; }
    public DbSet<Artist> Artists { get; set; }
    public DbSet<Album> Albums { get; set; }

    public SongDatabase()
    {
        Database.SetInitializer(new DropCreateDatabaseIfModelChanges<SongDatabase>());
    }
}

最后，这是我的 Song 类的代码。

public class Song
{
    public Song()
    {
        Album = new List<Album>();
    }

    /// <summary>
    ///  The Id of the song.
    /// </summary>
    public int SongId { get; set; }

    /// <summary>
    ///  The name of the song.
    /// </summary>
    public string SongName { get; set; }

    /// <summary>
    /// The artist of the song.
    /// </summary>
    public int ArtistId { get; set; }

    /// <summary>
    ///  The duration of the song.
    /// </summary>
    public double Duration { get; set; }

    /// <summary>
    ///  Whether or not this song should be excluded when calculating the total duration of the current playlist. 
    /// </summary>
    public bool Exclude { get; set; }

    /// <summary>
    /// Navigation property linking the album class to the song class.
    /// </summary>
    public virtual ICollection<Album> Album { get; set; }

    /// <summary>
    /// Navigation property linking the artist class to the song class.
    /// </summary>
    public virtual Artist Artist { get; set; }
}

Answer 1

您正在尝试在此处的代码中以静态值的形式访问 public DbSet<Song> Songs { get; set; }

[HttpPost]
public ActionResult Add(Song song)
{
    using (SongDatabase db = new SongDatabase())
    {
        SongDatabase.Songs.Add(song);
        SongDatabase.SaveChanges();
    }

    return RedirectToAction("Music");
}

您使用SongDatabase db = new SongDatabase() 创建了SongDatabase 的实例，但您没有使用该实例db。您应该将其更改为

[HttpPost]
public ActionResult Add(Song song)
{
    using (SongDatabase db = new SongDatabase())
    {
        db.Songs.Add(song);
        db.SaveChanges();
    }

    return RedirectToAction("Music");
}