C# 中的对象版本控制

Question

我在实体框架模型中有一些类，如下例所示：

public class Order
{
    public int Id { get; set; }
    public DateTime DateTime{ get; set; }
    public decimal TotalPrice { get; set; }
    public virtual ICollection<OrderItem> Items { get; set; }
}

public class OrderItem
{
    public int Id { get; set; }
    public Product Product { get; set; }
    public int Quantity { get; set; }
    public decimal TotalPrice { get; set; }
    public virtual ICollection<AddOn> AddOns { get; set; }
}

public class Product
{
    public int Id { get; set;}
    public string Name { get; set; }
    public decimal Price { get; set; }
}

public class AddOn
{
    public int Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}

在保存多次后，可以通过添加新项目/项目插件或删除其中一些来编辑订单及其相关项目，但我想保存订单对象的每个版本，并获取每个版本之间的差异。这样做的最佳做法是什么？

Answer 1

Order 实体没有自然键。使用有意义的 OrderNumber 属性，您可以将其与 OrderOn 结合使用作为版本化的自然键。

public class Order
{
    public int Id { get; set; }

    public string OrderNumber { get; set; } // <- add this property
    public DateTime OrderedOn { get; set; } // <- change this property name

    // OrderNumber, OrderedOn is a unique key

    public decimal TotalPrice { get; set; }
    public virtual ICollection<OrderItem> Items { get; set; }
}

您需要覆盖模型构建器，以便 EF 在数据库中创建唯一键约束：

[SuppressMessage("Microsoft.Design", "CA1063:ImplementIDisposableCorrectly", Justification = "IDisposable implemented as intended.")]
public class OrderingDbContext : DbContext, IDisposable
{
    private readonly IDatabaseInitializer<OrderingDbContext> _initializer;

    public OrderingDbContext(DbConnection connection) : this(connection, new NullDatabaseInitializer<OrderingDbContext>()) { }

    public OrderingDbContext(DbConnection connection,
        IDatabaseInitializer<OrderingDbContext> initializer)
        : base(connection, false)
    {
        _initializer = initializer;
    }

    public DbSet<Order> Orders { get; set; }
    // ...

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        Database.SetInitializer(_initializer);

        modelBuilder.Entity<Order>()
            .HasKey(o => new { o.OrderNumber, o.OrderedOn });

        base.OnModelCreating(modelBuilder);
    }

    #region IDisposable

    private bool _disposed;

    public new void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    private new void Dispose(bool disposing)
    {
        if (_disposed) return;
        if (disposing)
            base.Dispose();

        _disposed = true;
    }

    ~OrderingDbContext()
    {
        Dispose(false);
    }

    #endregion

}