EF Core 5.0 添加多对多使得一对多无法确定

Question

我想利用 ef core 5.0 中新的多对多功能。 https://docs.microsoft.com/en-us/ef/core/modeling/relationships?tabs=fluent-api%2Cfluent-api-simple-key%2Csimple-key

我现有的课程是

public class User : IdentityUser<int>
{
}

和

public class Notification
{
    public int ID { get; set; }
    public string Title { get; set; }
    public string Message { get; set; }
    public DateTime Created { get; set; }
    public DateTime Updated { get; set; }
    public User Creator { get; set; }
    public User Updater { get; set; }
    public Notification()
    {
    }
}

我想在它们之间添加一个多对多的关系，所以这些类是

public class User : IdentityUser<int>
{
    public ICollection<Notification> Notifications { get; set; }
}

和

public class Notification
{
    //[...]
    public ICollection<User> Recipients { get; set; }
}

现在dotnet ef migrations add NotificationRecipients导致Unable to determine the relationship represented by navigation 'Notification.Recipients' of type 'ICollection<User>'. Either manually configure the relationship, or ignore this property using the '[NotMapped]' attribute or by using 'EntityTypeBuilder.Ignore' in 'OnModelCreating'. Unable to determine the relationship represented by navigation 'Notification.Recipients' of type 'ICollection<User>'. Either manually configure the relationship, or ignore this property using the '[NotMapped]' attribute or by using 'EntityTypeBuilder.Ignore' in 'OnModelCreating'.

经过一番研究，我发现了[InverseProperty()]注释，所以我将它添加到 Notification.cs

public class Notification
{
    //[...]
    [InverseProperty("Notifications")]
    public ICollection<User> Recipients { get; set; }
}

多对多现在似乎已解决，但dotnet ef migrations add NotificationRecipients导致Unable to determine the relationship represented by navigation 'Notification.Creator' of type 'User'. Either manually configure the relationship, or ignore this property using the '[NotMapped]' attribute or by using 'EntityTypeBuilder.Ignore' in 'OnModelCreating'. Unable to determine the relationship represented by navigation 'Notification.Creator' of type 'User'. Either manually configure the relationship, or ignore this property using the '[NotMapped]' attribute or by using 'EntityTypeBuilder.Ignore' in 'OnModelCreating'.

是否有任何注释可以添加到Notification.Creator和Notification.Updater或任何其他方式来定义User和Notification之间的一对多关系？

我正在使用 MSSQL 作为数据库。

Answer 1

两个实体之间的多重关系通常不能自动确定，需要配置。 EF Core 中的许多东西（尤其是与关系相关的）只能使用流畅的 API 进行配置。

因此，与其寻找不存在或不直观的数据注释，不如简单地配置所需的关系（至少 - 导航属性和基数）：

modelBuilder.Entity<Notification>(builder =>
{
    builder.HasOne(e => e.Creator).WithMany();
    builder.HasOne(e => e.Updater).WithMany();
    builder.HasMany(e => e.Recipients).WithMany(e => e.Notifications);
});