代码之家 › 专栏 › 技术社区 › djdd87

实体框架代码优先-急加载未按预期工作?

code-first entity-framework-4 c#-4.0 linq-to-entities

djdd87 · 技术社区 · 14 年前

public class Customer
{
    public int Id {get;set;}
    public string Name {get;set;}

    public virtual ICollection<Order> Orders {get;set;}
}

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

    public virtual OrderType Type {get;set;}
    public virtual Customer Customer {get;set;}
} 

public class OrderType 
{
    public int Id {get;set;}
    public virtual ICollection<Order> Orders {get;set;}
}

问题是当我归还我的 ICollection<Order> 我要去接电话 Order 没关系,但是 OrderType 财产 订单

Id:          1
CustomerId:  1
Customer:    Populated
OrderTypeId: 3
Type:        null        // Never returned

我的映射代码如下所示:

public void ConfigureOrder(ModelBuilder builder)
{
    // Mapping from Order -> Customer
    builder.Entity<Order>()
        .HasRequired(x => x.Customer)
            .WithMany(x => x.Orders)
                .HasConstraint((order, cust) => order.CustomerId == cust.Id);

    // Mapping from Order -> OrderType
    builder.Entity<Order>()
        .HasRequired(x => x.OrderType)
            .WithMany(x => x.Orders)
                .HasConstraint((order, type) => order.OrderTypeId == type.Id);
}

然后在我的上下文中禁用了延迟加载:

public Context(string connectionString)
    : base(connectionString)
{
    ObjectContext.ContextOptions.LazyLoadingEnabled = false;
}

因此,要返回存储库中的数据,我使用 Include System.Data.Entity :

var query = from item in context.Customers
                .Include(x=> x.Orders)
            where item.Id == customerId
            select item;

我之所以这么想是因为我不能具体说明 Orders.OrderType ,这就是问题所在,所以我尝试了一些变体:

1 -> .Include(x=> x.Orders.FirstOrDefault().OrderType)
2 -> .Include("Orders")
3 -> .Include("Orders")
     .Include("Orders.OrderType")

var query = from item in context.Orders
                .Include(x=> x.OrderType)
            select item;

此代码将正确返回订单中的OrderType。

1 回复 | 直到 14 年前

djdd87 14 年前

哦,亲爱的。看来我是个十足的驴子。现在是17:45,反正我现在该回家了。

我有两种方法:

Get(int customerId)
{
    // This was the method I was testing within
    var query = from item in context.Customers
                    .Include("Orders.OrderType")
                select item;
}

Get(int customerId, int versionId)
{
    // This was the method that was running
    var query = from item in context.Customers
                    .Include(item.Orders)
                select item;
}

所以, "Orders.OrderType" 是正确的,尽管看起来很糟糕。我需要一些咖啡因。

编辑:

回到这个问题,includes最好的方法就是使用 System.Data.Entity

.Include(x=> x.Orders.Select(o=> o.OrderType));