c# - 外键实体框架问题

Question

我有一个父子实体：

public class Transaction
{
  public int TransactionId {get; set;}
  public int? OrderId {get; set;}
  public virtual Order Order {get; set;}

} 

public class Order 
{
  public int Id {get; set;}
  public virtual List<OrderItems> OrderItems {get; set;}
}

public class OrderItem
{
  public int Id {get; set;}
  public string Item {get; set;}
  public virtual int OrderId {get; set;}
  public virtual Order Order {get; set;}
}

上下文如下：

   modelBuilder.Entity<Transaction>( )
            .HasKey( x => x.TransactionId )
            .ToTable( "Transactions" );

        modelBuilder.Entity<Transaction>( )
            .HasOptional( x => x.Order )
            .WithMany( )
            .HasForeignKey( t => t.OrderId );

        modelBuilder.Entity<Order>( )
            .HasKey( o => o.Id )
            .ToTable("Orders");

        modelBuilder.Entity<OrderItem>( )
            .HasKey( i => i.Id )
            .ToTable( "OrderItems" );


        modelBuilder.Entity<OrderItem>( )
            .HasRequired( x => x.Order )
            .WithMany( o => o.OrderItems )
            .HasForeignKey( p => p.OrderId );

当我尝试创建事务类型的新实体时，类似于：

var transaction = new Transaction 
                   {TransactionId = Guid.NewGuid;
                    Order = new Order {OrderItems = new List<OrderItems>{Item="SunCream"}}};

和

ctx.Transactions.Add(transaction);
ctx.SaveChanges();

我明白了

INSERT 语句与 FOREIGN KEY 约束“FK_Transactions_Orders_OrderId”冲突。冲突发生在数据库“Transactions”、表“dbo.Orders”、“Id”列中。

我到底在这里做错了什么？

Answer 1

我相信在添加事务之前，您需要先将 Order 对象显式添加到 ctx 对象中。这样，当您调用.SaveChanges()上下文时，它将知道它必须先提交订单，然后再提交交易。