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c# - OnDelete 的 EF Core 注释

问题描述

我有一个注释问题：

        modelBuilder.Entity<FirstClass>()
            .HasOne(f => f.SecondClass)
            .WithOne(s => s.FirstClass)
            .HasForeignKey<FirstClass>(f => f.SecondClassId)
            .OnDelete(DeleteBehavior.Cascade);

如何用注释写这个？我没有找到 OnDelete 的注释。

标签： c#api.net-coreentity-framework-corefluent

解决方案

尝试这个 ：

你的模型


public class FirstClass
    {
        [Key]
        public int Id { get; set; } 
        public int SecondClassId { get; set; }

        [ForeignKey(nameof(SecondClassId))]
        [InverseProperty("FirstClasses")]
        public virtual SecondClass SecondClass { get; set; }
    }
    public class SecondClass
    {
        [Key]
        public int Id { get; set; }
        [InverseProperty(nameof(FirstClass.SecondClass))]
        public virtual ICollection<FirstClass> FirstClasses { get; set; }

    }

如果您只想拥有一个第一和一秒钟，请尝试此代码。但我不推荐它，因为很难找到错误。

public class FirstClass
    {
        [Key]
        public int Id { get; set; } 
        public int SecondClassId { get; set; }

        [ForeignKey(nameof(SecondClassId))]
        [InverseProperty("FirstClass")]
        public virtual SecondClass SecondClass { get; set; }
    }
    public class SecondClass
    {
        [Key]
        public int Id { get; set; }
        [InverseProperty(nameof(FirstClass.SecondClass))]
        public virtual FirstClass FirstClass { get; set; }

    }

您的数据库上下文：


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

        public FirstClassDbContext(DbContextOptions<FirstClassDbContext> options)
            : base(options)
        {
        }
        
        public DbSet<FirstClass> FirstClasses { get; set; }
        public DbSet<SecondClass> SecondClasses { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {

            optionsBuilder.UseSqlServer(@"Server=localhost;Database=FirstClass;Trusted_Connection=True;");
        }
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<FirstClass>(entity =>
            {
                entity.HasOne(d => d.SecondClass)
                   .WithMany(p => p.FirstClasses)
                   .HasForeignKey(d => d.SecondClassId)
                   .OnDelete(DeleteBehavior.ClientSetNull)
                   .HasConstraintName("FK_FirstClass_SecondClass");
            });

          // or for one to one you can use yours, but I don't recommend it since
//it will be hard to find the errors and it will not do anything for you. 
//Only confusing queries.

             modelBuilder.Entity<FirstClass>()
            .HasOne(f => f.SecondClass)
            .WithOne(s => s.FirstClass)
            .HasForeignKey(d => d.SecondClassId)
            .OnDelete(DeleteBehavior.ClientSetNull)
            .HasConstraintName("FK_FirstClass_SecondClass");
        }
    }

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