Entity Framework 具有多个连接条件的查询

Question

已编辑 我有表 Customers、Sites、Buildings 和 Addresses.

每个客户都有零个或多个（一个？）站点，每个站点恰好是一个客户的站点，即外键 Site.CustomerId 所指的站点。

同样，每个站点都有零个或多个建筑物，每个建筑物恰好在一个站点上，即外键Building.SiteId所指的站点。

最后：每个customer/site/building只有一个地址，即外键Customer.CustomerPhysicalAddressId、Site.AddressId、Building.BuildingAddressId所指向的地址。

我也有一个string searchText

我想要所有具有至少以下一项的客户的 ID：

a CustomerName 类似于 searchText
至少一个 SiteName 类似 searchText
至少一个 BuildingName 类似 searchText
一个PhysicalAddress喜欢searchText
其所有 Sites 中至少有一个 SiteAddress 类似于 searchText
其所有 Buildings 中至少有一个 BuildingAddress 类似于 searchText

对于上述要求，我有这个 SQL 查询逻辑

SELECT DISTINCT c.customerID 
FROM Customer AS c
LEFT OUTER JOIN Site AS s ON s.customerId = c.customerID
LEFT OUTER JOIN Building AS b ON s.Id = b.siteId
LEFT OUTER JOIN Address AS A ON A.addressId = c.customerPhysicalAddressID 
                             OR A.addressId = s.AddressId 
                             OR A.addressId = b.buildingAddressId
WHERE 
    c.customerName LIKE '%searchText%' 
    OR c.SiteName LIKE '%searchText%' 
    OR b.buildingName LIKE '%searchText%' 
    OR A.Street LIKE '%searchText%'

控制器 class 在编写 linq 查询时出现问题。

我的Linq查询是这样写的

if (!string.IsNullOrEmpty(searchText))
{
    var resultQuery = from customer in this.DatabaseContext.Customers
                      join site in this.DatabaseContext.Sites
                           on customer.customerID equals site.CustomerId into customer_site_group
                      from customer_site in customer_site_group.DefaultIfEmpty()
                      join building in this.DatabaseContext.Buildings
                           on customer_site.Id equals building.siteId into site_building_group
                      from site_building in site_building_group.DefaultIfEmpty()
                      join A in this.DatabaseContext.Addresses
                             on new
                               {
                                   key1 = customer.customerPhysicalAddressID,
                                   key2 = customer_site.AddressId,
                                   key3 = site_building.buildingAddressID
                               }
                               equals new
                               {
                                    key1 = A.addressID ||
                                    key2 = A.addressID ||
                                    key3 = A.addressID
                               } into Address_site_building
                      where (customer.customerName.Contains(searchText) ||
                             customer_site.siteName.Contains(searchText) ||
                             site_building.buildingName.Contains(searchText) ||
                             A.street.Contains(searchText))
                      select new
                             {
                                   customerID = customer.customerID
                             };
}

在结果查询中我只想让customer Id满足以上条件。在引入 Addresses 实体之前，linq 查询工作正常。面对写多个on条件，LinqPad报错

The type of one of the expression in the join clause is incorrect. Type reference failed in the call to GroupJoin

我是 EF 和 linq 的新手 - 只是尝试和理解它。

感谢任何宝贵的意见和回答。

Answer 1

所以你有 Customers、Sites、Buildings 和 Addresses 的表格。

每个客户都有零个或多个（一个？）站点，每个站点恰好是一个客户的站点，即外键 Site.CustomerId 所指的站点。

同样，每个Site都有零个或多个建筑物，每个建筑物恰好在一个Site上，即外键Building.SiteId所指的Site。

最后：每个Customer/Site/Building都有一个Address，即外键Customer.CustomerPhysicalAddressId、Site.AddressId、Building.BuildingAddressId所指的Address。

你还有一个string searchText.

您需要具有至少以下一项的所有客户的 ID：

类似于 searchText 的 CustomerName
至少一个类似于 searchText
至少一个 BuildingName 类似于 searchText
像搜索文本这样的物理地址
他的所有站点中至少有一个站点地址类似于 searchText
他所有建筑物中至少有一个类似于 searchText 的 BuildingAddress。

我的建议是，从每个客户那里获取他的 ID，以及包含以下字符串的序列：

客户姓名
他的实际地址
他所有站点和建筑物的名称
他所有站点和建筑物的地址

结果是 [CustomerId，字符串序列] 的序列。您只想保留那些 CustomerId，其中“字符串序列”中至少有一个字符串类似于 searchText。

创建 [CustomerId, 字符串序列] 组合并不困难。尝试实现“like searchText”时遇到问题。

让我们先创建组合。

每当你有“项目及其子项目”，并且你想将它们视为一个项目序列时，请考虑使用 Queryable.SelectMany.

的重载之一

var result = dbContext.Customers.SelectMany(customer => customer.Sites,

// parameter resultSelector: take every Customer with its Site to create one new:
(customer, sitesOfThisCustomer) => new
{
    Id = customer.Id,

    // the searchTexts: the customer name, his physical address
    // the names and address of of all his Sites
    // and the names and addresses of all the building of each side (inner SelectMany)
    SearchTexts = new string[] {customer.CustomerName, customer.PhysicalAddress}

    .Concat (sitesOfThisCustomer.SelectMany(site => site.Buildings,
    (site, buildingsOfThisSite) => new string[] {site.SiteName, site.SiteAddress}
        .Concat(buildingsOfThisSite.SelectMany(building => new string[]
            {building.BuildingName, building.BuildingAddress})));

我不确定 new string[] {...} 是否适用于 IQueryable，如果不能，请考虑另一种方法如何使用名称和地址创建可枚举序列 (Enumerable.Repeat? with repeat数 1?)

所以现在您拥有每个客户的 ID 和一大串客户的姓名和地址、他的站点以及这些站点上的建筑物。您所要做的就是为 Like searchText 添加一个 .Where。据我所知，标准 LINQ 没有这个，但也许你可以这样做：

.Where(customeWithSearchTexts => customerWithSearchTexts.SearchTexts
    .Any(text => text.StartsWith(searchText));

在上面的解决方案中，我使用了您在 entity framework 中看到的 virtual ICollection<...>。如果你不能使用它，因为你的类没有这个，你将不得不自己加入群组：

var result = customers.SelectMany(

    // the Sites of this customre
    customer => dbContext.Sites.Where(site.CustomerId == customer.Id),

    // resultSelector:
    (customer, sitesOfThisCustomer) => ...

        // inner selectmany
        site.SelectMany(dbContext.Buildings.Where(building.SiteId == site.Id),

        ...

Answer 2

如果您看到 SQL 查询可以重写为

，答案可能很明显

SELECT DISTINCT c.customerID 
FROM Customer AS c
LEFT OUTER JOIN Site AS s ON s.customerId = c.customerID
LEFT OUTER JOIN Building AS b ON s.Id = b.siteId
, Address AS A
WHERE 
    (c.customerName LIKE '%searchText%' 
    OR c.SiteName LIKE '%searchText%' 
    OR b.buildingName LIKE '%searchText%' 
    OR A.Street LIKE '%searchText%')
AND (A.addressId = c.customerPhysicalAddressID 
    OR A.addressId = s.AddressId
    OR A.addressId = b.buildingAddressId)

即连接变成了 WHERE 子句。然后 LINQ 翻译变成类似

from customer in this.DatabaseContext.Customers
join site in this.DatabaseContext.Sites
    on customer.customerID equals site.CustomerId into customer_site_group
from customer_site in customer_site_group.DefaultIfEmpty()
join building in this.DatabaseContext.Buildings
    on customer_site.Id equals building.siteId into site_building_group
from site_building in site_building_group.DefaultIfEmpty()
from A in this.DatabaseContext.Addresses
where (customer.customerPhysicalAddressID = A.addressID
       || customer_site.AddressId = A.addressID
       || site_building.buildingAddressID = A.addressID)
where (customer.customerName.Contains(searchText) ||
     customer_site.siteName.Contains(searchText) ||
     site_building.buildingName.Contains(searchText) ||
     A.street.Contains(searchText))
select new
{
    customerID = customer.customerID
};

一般建议（请参阅我的评论）：尝试通过引入导航属性从 LINQ 查询中删除连接。

Entity Framework 具有多个连接条件的查询

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