如何使 C# Linq 查询语法等效于 ThenInclude 的方法语法？

Question

我正在尝试将方法语法转换为查询语法。

类结构嵌套如下：

1. 财产
2. 物业方
3. 聚会
4. 派对邮寄地址
5. PropertyMailingAddress

与查询语法相比，MethodSyntax（第一个）似乎带来了更少的行分组，带来了更多的行。

如何将第二个查询语法修复为等同于方法语法？

var result = db.Property.Include(pm => pm.PropertyParty)
                    .Include(pm => pm.PropertyParty)
                    .ThenInclude(x => x.Party)
                    .ThenInclude(x => x.PartyMailingAddress)
                    .ThenInclude(x => x.PropertyMailingAddress)
                    .ToList();

var testingResult = (from property in db.Property
                     join propertyParty in db.PropertyParty
                        on property.PropertyId equals propertyParty.PropertyId
                     join party in db.Party
                        on propertyParty.PartyId equals party.PartyId
                     join partyMailingAddress in db.PartyMailingAddress
                        on party.PartyId equals partyMailingAddress.PartyId
                     join propertyMailingAddress in db.PropertyMailingAddress
                        on partyMailingAddress.PartyMailingAddressId equals propertyMailingAddress.PartyMailingAddressId
                     select property).ToList();

*如果没有等价物，我可以抓取查询结果，并将它们分组为类似于方法语法吗？

查询语法答案不应包含 ThenInclude

目前使用的是 Net Core 2.2

Answer 1

Include 没有特殊的 LINQ 语法。所以等价不是一堆连接。这是

var q = from p in db.Property
                    .Include(pm => pm.PropertyParty)
                    .Include(pm => pm.PropertyParty)
                    .ThenInclude(x => x.Party)
                    .ThenInclude(x => x.PartyMailingAddress)
                    .ThenInclude(x => x.PropertyMailingAddress)
        select p;

var testingReqult = p.ToList();

Answer 2

您在查询语法中看到更多行的原因是因为您正在执行连接，而方法一正在执行包含仅加载相关实体的操作（检查 this）。

如果你真的需要将它与查询结合起来，你可以这样做：

(from property in db.Property 
 select property)
    .Include(pm => pm.PropertyParty)
    .Include(pm => pm.PropertyParty)
    .ThenInclude(x => x.Party)
    .ThenInclude(x => x.PartyMailingAddress)
    .ThenInclude(x => x.PropertyMailingAddress)
    .ToList();

---

如果您正在寻找 group by，因为您想坚持使用查询语法，它会是这样的（但对我来说，所有这些工作似乎都不值得）

var testingResult = (from property in db.Property
                     join propertyParty in db.PropertyParty
                        on property.PropertyId equals propertyParty.PropertyId
                     join party in db.Party
                        on propertyParty.PartyId equals party.PartyId
                     join partyMailingAddress in db.PartyMailingAddress
                        on party.PartyId equals partyMailingAddress.PartyId
                     join propertyMailingAddress in db.PropertyMailingAddress
                        on partyMailingAddress.PartyMailingAddressId equals propertyMailingAddress.PartyMailingAddressId
                     group property by new { property.Field1, x.Field2, ... /* Group by all the property fields */ } into grouped
                     select new Property 
                     {
                        Field1 = grouped.Key.Field1,
                        Field2 = grouped.Key.Field2,
                        ... /* Manually populate all the properties */
                        PropertyParties = grouped.Select(x => x.PropertyParties),
                        ... /* Manually populate all the related entities */
                     }).ToList();