Question

我正在尝试为我想在视图中显示的数据创建一个ViewModel。问题是，显示的数据分布在2个数据库中，每个数据库中有多个表。我已经读过你不能在多个上下文中加入Linq查询，这是有道理的，而且我还读到我们不能在EF5中使用Code-First来使用存储过程....这导致我使用3个不同的Linq查询并尝试将它们组合成1个ViewModel ......我只是不确定如何到达那里。

这是我的Linq查询：

var csdContext = new CSDContext(CustomerCode);
var masterContext = new MasterContext();

//Only returns 1 row - which is what we want.
List<Site> sites = (from s in csdContext.Sites
                join sa in csdContext.SiteAddresses
                    on s.SiteID equals sa.SiteID
                join a in csdContext.Addresses
                    on sa.AddressID equals a.AddressID
                join spv in csdContext.SiteProductVersions
                    on s.SiteID equals spv.ProductVersionID
                where s.SiteID == id
                select s).ToList();

//List
List<States> states = (from s in masterContext.StatesTable
                    select s).ToList();

我的ViewModel如下所示：

public class SiteDetailsViewModel
{
    public string Address { get; set; }
    public string Address2 { get; set; }
    public string City { get; set; }
    public string StateCode { get; set; }
    public string ZipCode { get; set; }
    public string OfficePhone { get; set; }
    public string MobilePhone { get; set; }
    public string AlternativePhone { get; set; }
    public int ProductVersionID { get; set; }
}

基本上，我需要这些表格中的以下数据：
csdContext - 地址
地址
地址2
市
ZipCode

csdContext - 网站
OfficePhone
MobilePhone
AlternativePhone

csdContext - SiteProductVersions
ProductVersionID

masterContext - States
StateCode

以下是SQL在SQL中的连接方式：

SELECT csd_a.Address, csd_a.Address2, csd_a.City, mstr_st.StateCode, csd_a.ZipCode, csd_s.OfficePhone, csd_s.MobilePhone, 
csd_s.AlternativePhone, csd_spv.ProductVersionID
FROM CSD.dbo.Sites AS csd_s 
INNER JOIN  CSD.dbo.SiteAddress AS csd_sa ON csd_sa.SiteID = csd_s.SiteID 
INNER JOIN  CSD.dbo.Address AS csd_a ON csd_a.AddressID = csd_sa.AddressID 
INNER JOIN CSD.dbo.SiteProductVersions AS csd_spv ON csd_s.SiteID = csd_spv.SiteID 
INNER JOIN MasterDB.dbo.States AS mstr_st ON mstr_st.StateID = csd_a.StateID

我无法弄清楚如何合并这3个结果来为SiteDetailsViewModel创建ViewModel数据。有人可以帮忙吗？

Answer 1

如果按照OP中的描述实现查询，可以使用：

var query = sites.Join(
            states,
            si => si.StateID,
            st => st.StateID,
           (si, st) => new SiteDetailsViewModel
                        {
                             Address = si.Address,
                             Address2 = si.Address2,
                             City = si.City,
                             StateCode = st.StateCode,
                             ZipCode = si.ZipCode,
                             OfficePhone = si.OfficePhone,
                             MobilePhone = si.MobilePhone,
                             AlternativePhone = si.AlternativePhone,
                             ProductVersionID = siProductVersionID
                        });

Answer 2

那么你为什么不这样写呢：

from ...
...
where s.SiteID == id
select new SiteDetailsViewModel()
{
    Address = sa.Address,
    Address2 = as.Address2,
    ..
}

从多个上下文加入LINQ查询

2 个答案: