c# - 使用 Entity Framework Core 在具有多对多关系的数据透视表中插入新记录

Question

我正在使用 ASP.NET Core MVC 构建应用程序。我正在尝试插入一条具有多对多关系的新记录。我有 3 个表 Repairs、Parts 和 RepairParts。

如何将 RepairId 和 PartId 插入到 RepairParts 表中？ EF Core 是否为此提供了一些东西？我搜索了文档，但它没有提到如何执行此操作。

Entity Framework 会自动执行此操作吗？ (插入到数据透视表)还是我需要手动执行？一个例子会有所帮助。

维修类:

public class Repair
{
    [Key]
    public int RepairId { get; set; }

    public int VehicleId { get; set; }
    public string Notes { get; set; }
    public string Mileage { get; set; }
    public DateTime RepairDate { get; set; }
    public string uuid { get; set; }

    [ForeignKey("VehicleId")]
    public Vehicle Vehicle { get; set; }

    public virtual ICollection<RepairParts> RepairParts { get; set; }
}

部分类:

public class Part
{
    public int PartId { get; set; }
    public int Code { get; set; }
    public string PartCode { get; set; }
    public string Type { get; set; }
    public string Name { get; set; }
    public string Descr { get; set; }
    public string Manufacturer { get; set; }
    public string uuid { get; set; }

    public virtual ICollection<RepairParts> RepairParts { get; set; }
}

RepairPart 类:

public class RepairParts
{
    public int RepairId { get; set; }
    public Repair Repair { get; set; }

    public int PartId { get; set; }
    public Part Part { get; set; }

    public decimal price { get; set; }
}

DbContext 类:

public class ApplicationDbContext : IdentityDbContext
{
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
        : base(options)
    {
    }

    public DbSet<Customer> Customers { get; set; }
    public DbSet<TaxOffice> TaxOffices { get; set; }
    public DbSet<Vehicle> Vehicles { get; set; }
    public DbSet<Part> Parts { get; set; }
    public DbSet<Repair> Repairs { get; set; }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);

        builder.Entity<Customer>()
              .HasMany(v => v.Vehicles)
              .WithOne(b => b.Customer);

        builder.Entity<Vehicle>()
             .HasOne(c => c.Customer)
             .WithMany(b => b.Vehicles);

        builder.Entity<Vehicle>()
              .HasMany(v => v.Repairs)
              .WithOne(c => c.Vehicle);

        builder.Entity<RepairParts>()
            .HasKey(t => new { t.RepairId, t.PartId });

        builder.Entity<RepairParts>()
            .HasOne(r => r.Repair)
            .WithMany(t => t.RepairParts)
            .HasForeignKey(f => f.RepairId);

        builder.Entity<RepairParts>()
            .HasOne(r => r.Part)
            .WithMany(p => p.RepairParts)
            .HasForeignKey(f => f.PartId);
    }
}

Answer 1

这里有两个选项供您选择:

1. 插入RepairParts通过public virtual ICollection<RepairParts> RepairParts { get; set; }

   var repaire = new Repair { uuid = "R3" };
   var part = new Part { Code = 3 };
   var reparePart = new RepairParts { Repair = repaire, Part = part };
   repaire.RepairParts = new List<RepairParts>()
   {
       reparePart
   };
   _context.Add(repaire);
   _context.SaveChanges();
   

2. 插入RepairParts明确由_context.Add(reparePart1);

   var repaire1 = new Repair { uuid = "RR1" };
   var part1 = new Part { Code = 4 };
   var reparePart1 = new RepairParts { Repair = repaire1, Part = part1 };
   _context.Add(repaire1);
   _context.Add(part1);
   _context.Add(reparePart1);
   _context.SaveChanges();