Question

您好，

我采用一个经典的例子，我有一个Customer表和Purchase表，一个客户可以有多个订单。

我创建了一个DBML文件，然后从“服务器资源管理器窗口”中删除了两个表到DBML编辑器，生成了两个实体：Customers和Purchases

我有一些对象：

public interface IMyCustomer
{
    int Id { get; set; }
    string Code { get; set; }
    string Firstname { get; set; }
    string Lastname { get; set; }
    List<IMyPurchase> Purchases { get; set; }
}

public class MyCustomer : IMyCustomer
{
    public int Id { get; set; }
    public string Code { get; set; }
    public string Firstname { get; set; }
    public string Lastname { get; set; }
    public List<IMyPurchase> Orders { get; set; }
}

public interface IMyPurchase
{
    int Id { get; set; }
    string Code { get; set; }
    DateTime CreationDate { get; set; }
}

public class MyPurchase : IMyPurchase
{
    public int Id { get; set; }
    public string Code { get; set; }
    public DateTime CreationDate { get; set; }
}

var result = 
    from customer in _dataContext.Customers
    join order in _dataContext.Purchases on customer.Id equals order.IdCustomer
    select new MyCustomer
    {
        Code = customer.Code,
        Firstname = customer.Firstname,
        Lastname = customer.Lastname,
        Id = customer.Id,
        Purchases = _dataContext.Purchases
            .Select(x => x.IdCustomer == customer.Id)
            .Cast<IMyPurchase>()
            .ToList<IMyPurchase>()
    };

linq查询工作。对于结果条目，我拥有关于customer的所有信息，我在Purchases中有正确的行数，但Purchases的每个条目的每个属性都为空。我想加载Customer信息和所有purchase

有什么想法吗？

谢谢，

Answer 1

您似乎在Purchase和MyPurchase之间没有任何翻译逻辑。

此外Cast<>()方法将尝试使用隐式转换，但除非您的Linq-to-SQL实体实现该接口，否则无法以这种方式转换。

我的建议是使用AutoMapper之类的内容或在你的linq语句中添加翻译逻辑（类似于你对MyCustomer所做的事情）。类似的东西：

var result = 
    from customer in _dataContext.Customers
    join order in _dataContext.Purchases on customer.Id equals order.IdCustomer
    select new MyCustomer
    {
        Code = customer.Code,
        Firstname = customer.Firstname,
        Lastname = customer.Lastname,
        Id = customer.Id,
        Purchases = _dataContext.Purchases
            .Where(x => x.IdCustomer == customer.Id)
            .Select(x => new MyPurchase {
                Id = x.Id,
                Code = x.Code,
                CreationDate = x.CreationDate
            }).ToList();
    };

Answer 2

以下是一个示例，以及您在购买中的客户ID

    var items = (from p in _dataContext.Purchases
                 join c in _dataContext.Customers
                 on p.CustomerID equals c.ID
                 where (c.ID == customerId)
                 orderby p.CreationDate descending
                 select new { p, c });

foreach (var data in items)
{
    // do stuff
    int customerId = data.c.ID;
    int purchaseId = data.p.ID;
    // you can acces all properties of both objects
}

Linq2SQL得到了孩子

2 个答案: