实体框架无法插入数据答案

【问题标题】：Entity Framework cannot insert data实体框架无法插入数据
【发布时间】：2021-10-31 23:14:19
【问题描述】：

我正在将此作为一个学校项目，而且我是第一次使用实体框架，所以不要太苛刻。这些是我的表/类。

public class Database : DbContext
{
    public Database() {} 

    public DbSet<Producer> Producers { get; set; } 
    public DbSet<Song> Songs { get; set; }
    public DbSet<ProducerSong> ProducerGlasbos { get; set; }
}

public class Song
{
    public int Id { get; set; }
    
    public string Title { get; set; }
    public int Length { get; set; }
    public int Views { get; set; }
}

public class Producer
{
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public int Id { get; set; }
    
    public string name { get; set; }
    public string surname { get; set; }
    public int birth { get; set; }
}

public class ProducerSong
{
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public int Id { get; set; }
    
    public Producer Producer { get; set; }
    public Song Songs { get; set; }
    
    public int year { get; set; }
}

当我尝试将类的新实例插入表/数据库时，只是崩溃并抛出错误

Data.Glasbas.Add(new Glasba { length = 200, Naslov = "Bolecina", views= 313});

错误截图：Look at me

感谢您的帮助。

【问题讨论】：

标签： c# entity-framework

【解决方案1】：

public class Database : DbContext
{
    public Database() { }
    public DbSet<Producer> Producers { get; set; }
    public DbSet<Song> Songs { get; set; }
    public DbSet<ProducerSong> ProducerGlasbos { get; set; }

    public class ProducerSong
    {
        [System.ComponentModel.DataAnnotations.Key]
        public int ProducerSongID { get; set; }

        public Producer Producer { get; set; }
        public Song Songs { get; set; }
        public int year { get; set; }
    }

    public class Song
    {
        [System.ComponentModel.DataAnnotations.Key]
        public int Id { get; set; }

        public string Title { get; set; }
        public int lenght { get; set; }
        public int views { get; set; }

        //ForeignKey
        public int ProducerSongID { get; set; }
        public ProducerSong ProducerSong { get; set; }
    }

    public class Producer
    {
        [System.ComponentModel.DataAnnotations.Key]
        public int Id { get; set; }

        public string name { get; set; }
        public string surname { get; set; }
        public int birth { get; set; }

        //ForeignKey
        public int ProducerSongID { get; set; }
        public ProducerSong ProducerSong { get; set; }
    }
}

【讨论】：

【解决方案2】：

问题出在构造函数中

【讨论】：

此答案似乎与您的原始问题不符。您的所有类都不包含构造函数。另外，这是 constructors 的普遍问题，还是只有需要 parameters 的构造函数？