c# - 如何删除带有外键约束的记录？

Question

启动一个新的 ASP.NET MVC 3 应用程序并收到以下错误:

The primary key value cannot be deleted because references to this key still exist.

如何解决？

模型(EF 代码优先)

public class Journal
{
    public int JournalId { get; set; }
    public string Name { get; set; }
    public virtual List<JournalEntry> JournalEntries { get; set; }
}
public class JournalEntry
{
    public int JournalEntryId { get; set; }
    public int JournalId { get; set; }
    public string Text { get; set; }
}

Controller

//
// POST: /Journal/Delete/5

[HttpPost, ActionName("Delete")]
public ActionResult DeleteConfirmed(int id)
{            
    Journal journal = db.Journals.Find(id);
    db.Journals.Remove(journal);
    db.SaveChanges(); // **exception occurs here**
    return RedirectToAction("Index");
}

数据库设置

public class FoodJournalEntities : DbContext
{
    public DbSet<Journal> Journals { get; set; }
    public DbSet<JournalEntry> JournalEntries { get; set; }
}

Answer 1

找到解决方案:

public class FoodJournalEntities : DbContext
{
    public DbSet<Journal> Journals { get; set; }
    public DbSet<JournalEntry> JournalEntries { get; set; }
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Journal>()
               .HasOptional(j => j.JournalEntries)
               .WithMany()
               .WillCascadeOnDelete(true);
        base.OnModelCreating(modelBuilder);
    }
}

Source