Rafy 中的 Linq 查询支持（根据聚合子条件查询聚合父）

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Rafy 中的 Linq 查询支持（根据聚合子条件查询聚合父）
为了提高开发者的易用性，Rafy 领域实体框架在很早开始就已经支持使用 Linq 语法来查询实体了。但是只支持了一些简单的、常用的条件查询，支持的力度很有限。特别是遇到对聚合对象的查询时，就不能再使用 Linq，而只能通过构造底层查询树的接口来完成了。由于开发者的聚合查询的需求越来越多，所以本周我们将这部分进行了增强。

接下来，本文将说明 Rafy 框架原来支持的 Linq 语法，以及最新加入的聚合查询支持及用法。

使用 Linq 查询的代码示例
public WarehouseList GetByCode(string warehouseCode, string nameKeywords, PagingInfo pagingInfo)

{

return this.FetchList(r => r.DA_GetByCode(warehouseCode, nameKeywords, pagingInfo));

}

private EntityList DA_GetByCode(string warehouseCode, string nameKeywords, PagingInfo pagingInfo)

{

var q = this.CreateLinqQuery();

//条件对比

q = q.Where(e => e.Code == warehouseCode);

if (!string.IsNullOrEmpty(nameKeywords))

{

q = q.Where(e => e.Name.Contains(nameKeywords));

}

//排序

q = q.OrderByDescending(w => w.Name);

return this.QueryList(q, pagingInfo);//以指定的分页信息 pagingInfo 分页

}
```
 
```
支持的一般查询

使用 CreateLinqQuery 方法创建出一个 IQueryable<Warehouse> 对象，针对该对象，我们可以以下的标准 Linq 方法：Where、OrderBy、OrderByDescending、ThenBy、ThenByDescending、Count。

对于其中最重要的 Where 方法，Rafy 也支持许多操作，包括：
- 属性的各种对比操作（=,!=,>,>=,<,<=,!,Contains,StartsWith,EndsWith等）。
- 支持两个属性条件间的连接条件：&&、||。
- 支持引用查询。即间接使用引用实体的属性来进行查询，在生成 Sql 语句时，将会生成 INNER JOIN 语句，连接上这些被使用的引用实体对应的表。例如：
  q = q.Where(warehouse => warehouse.Administrator.Name == "admin");
这部分的内容，之前的版本已经支持了，各位可参见 Rafy 框架的用户手册。

聚合查询

聚合查询的功能是，开发者可以通过定义聚合子的属性的条件，来查询聚合父。这是本次升级的重点。

例如，书籍管理系统中，Book （书）为聚合根，它拥有 Chapter （章）作为它的聚合子实体，而 Chapter 下则还有 Section（节）。那么，我们可以通过这个功能，来查询类似以下需求的数据：
- 查询拥有某个章的名字的所有书籍。
要实现这种场景的查询，我们可以在仓库的数据层，使用下面的 Linq 语法：
public BookList LinqGetIfChildrenExists(string chapterName)

{

return this.FetchList(r => r.DA_LinqGetIfChildrenExists(chapterName));

}

private EntityList DA_LinqGetIfChildrenExists(string chapterName)

{

var q = this.CreateLinqQuery();

q = q.Where(book => book.ChapterList.Concrete().Any(c => c.Name == chapterName));

q = q.OrderBy(b => b.Name);

return this.QueryList(q);

}
其生成的 Sql 如下：
```
SELECT [T0].[Id], [T0].[Author], [T0].[BookCategoryId], [T0].[BookLocId], [T0].[Code], [T0].[Name], [T0].[Price], [T0].[Publisher]
FROM [Book] AS [T0]
WHERE EXISTS (
    SELECT 1
    FROM [Chapter] AS [T1]
    WHERE [T1].[BookId] = [T0].[Id] AND [T1].[Name] = @p0
)
ORDER BY [T0].[Name] ASC
```
- 查询每个章的名字必须满足某条件的所有书籍。
我们可以在仓库的数据层，使用下面的 Linq 语法：
public BookList LinqGetIfChildrenAll(string chapterName)

{

return this.FetchList(r => r.DA_LinqGetIfChildrenAll(chapterName));

}

private EntityList DA_LinqGetIfChildrenAll(string chapterName)

{

var q = this.CreateLinqQuery();

q = q.Where(e => e.ChapterList.Cast<Chapter>().All(c => c.Name == chapterName));

q = q.OrderBy(e => e.Name);

return this.QueryList(q);

}
生成的 SQL 是：
```
SELECT [T0].[Id], [T0].[Author], [T0].[BookCategoryId], [T0].[BookLocId], [T0].[Code], [T0].[Name], [T0].[Price], [T0].[Publisher]
FROM [Book] AS [T0]
WHERE NOT (EXISTS (
    SELECT 1
    FROM [Chapter] AS [T1]
    WHERE [T1].[BookId] = [T0].[Id] AND [T1].[Name] != @p0
))
ORDER BY [T0].[Name] ASC
```
- 查询某个章中所有节必须满足某条件的所有书籍。
我们可以在仓库的数据层，使用下面的 Linq 语法：
public BookList LinqGetIfChildrenExistsSectionName(string sectionName)

{

return this.FetchList(r => r.DA_LinqGetIfChildrenExistsSectionName(sectionName));

}

private EntityList DA_LinqGetIfChildrenExistsSectionName(string sectionName)

{

var q = this.CreateLinqQuery();

q = q.Where(book => book.ChapterList.Concrete().Any(c => c.SectionList.Cast<Section>().Any(s => s.Name.Contains(sectionName))));

q = q.OrderBy(b => b.Name);

return this.QueryList(q);

}
将会生成如下 SQL：
```
SELECT [T0].[Id], [T0].[Author], [T0].[BookCategoryId], [T0].[BookLocId], [T0].[Code], [T0].[Name], [T0].[Price], [T0].[Publisher]
FROM [Book] AS [T0]
WHERE EXISTS (
    SELECT 1
    FROM [Chapter] AS [T1]
    WHERE [T1].[BookId] = [T0].[Id] AND EXISTS (
        SELECT 1
        FROM [Section] AS [T2]
        WHERE [T2].[ChapterId] = [T1].[Id] AND [T2].[Name] LIKE @p0
    )
)
ORDER BY [T0].[Name] ASC
```
- 同时，这些查询也可以支持分页。例如，我们在上面的查询添加一个分页条件，代码如下：
public BookList LinqGetIfChildrenExistsSectionName(string sectionName)

{

return this.FetchList(r => r.DA_LinqGetIfChildrenExistsSectionName(sectionName));

}

private EntityList DA_LinqGetIfChildrenExistsSectionName(string sectionName)

{

var q = this.CreateLinqQuery();

q = q.Where(book => book.ChapterList.Concrete().Any(c => c.SectionList.Cast<Section>().Any(s => s.Name.Contains(sectionName))));

q = q.OrderBy(b => b.Name);

return this.QueryList(q, new PagingInfo(2, 1));//分页

}
分成的 SQL 如下：
```
SELECT TOP 1 [T0].[Id], [T0].[Author], [T0].[BookCategoryId], [T0].[BookLocId], [T0].[Code], [T0].[Name], [T0].[Price], [T0].[Publisher]
FROM [Book] AS [T0]
WHERE EXISTS (
    SELECT 1
    FROM [Chapter] AS [T1]
    WHERE [T1].[BookId] = [T0].[Id] AND EXISTS (
        SELECT 1
        FROM [Section] AS [T2]
        WHERE [T2].[ChapterId] = [T1].[Id] AND [T2].[Name] LIKE @p0
    )
) AND [T0].[Id] NOT IN (
    SELECT TOP 1 [T0].[Id]
    FROM [Book] AS [T0]
    WHERE EXISTS (
        SELECT 1
        FROM [Chapter] AS [T1]
        WHERE [T1].[BookId] = [T0].[Id] AND EXISTS (
            SELECT 1
            FROM [Section] AS [T2]
            WHERE [T2].[ChapterId] = [T1].[Id] AND [T2].[Name] LIKE @p1
        )
    )
    ORDER BY [T0].[Name] ASC
)
ORDER BY [T0].[Name] ASC
```
头晕，越来越复杂……不过经过测试，上面都没有什么问题。

下面是一个单元测试生成的分页、复杂聚合查询的 SQL，贴上来观赏下：
```
SELECT TOP 2 [T0].[Id], [T0].[Author], [T0].[BookCategoryId], [T0].[BookLocId], [T0].[Code], [T0].[Name], [T0].[Price], [T0].[Publisher]
FROM [Book] AS [T0]
    LEFT OUTER JOIN [BookCategory] AS [T1] ON [T0].[BookCategoryId] = [T1].[Id]
WHERE [T0].[Name] != @p0 AND [T1].[Name] = @p1 AND EXISTS (
    SELECT 1
    FROM [Chapter] AS [T2]
    WHERE [T2].[BookId] = [T0].[Id] AND [T2].[Name] = @p2
) AND EXISTS (
    SELECT 1
    FROM [Chapter] AS [T3]
    WHERE [T3].[BookId] = [T0].[Id] AND [T3].[Name] = @p3 AND NOT (EXISTS (
        SELECT 1
        FROM [Section] AS [T4]
            LEFT OUTER JOIN [SectionOwner] AS [T5] ON [T4].[SectionOwnerId] = [T5].[Id]
        WHERE [T4].[ChapterId] = [T3].[Id] AND ([T4].[Name] NOT LIKE @p4 OR [T4].[SectionOwnerId] IS NULL OR [T5].[Name] != @p5)
    ))
) AND [T0].[Id] NOT IN (
    SELECT TOP 4 [T0].[Id]
    FROM [Book] AS [T0]
        LEFT OUTER JOIN [BookCategory] AS [T1] ON [T0].[BookCategoryId] = [T1].[Id]
    WHERE [T0].[Name] != @p6 AND [T1].[Name] = @p7 AND EXISTS (
        SELECT 1
        FROM [Chapter] AS [T2]
        WHERE [T2].[BookId] = [T0].[Id] AND [T2].[Name] = @p8
    ) AND EXISTS (
        SELECT 1
        FROM [Chapter] AS [T3]
        WHERE [T3].[BookId] = [T0].[Id] AND [T3].[Name] = @p9 AND NOT (EXISTS (
            SELECT 1
            FROM [Section] AS [T4]
                LEFT OUTER JOIN [SectionOwner] AS [T5] ON [T4].[SectionOwnerId] = [T5].[Id]
            WHERE [T4].[ChapterId] = [T3].[Id] AND ([T4].[Name] NOT LIKE @p10 OR [T4].[SectionOwnerId] IS NULL OR [T5].[Name] != @p11)
        ))
    )
    ORDER BY [T0].[Name] ASC
)
ORDER BY [T0].[Name] ASC
```
刚开始支持 Linq 查询的时候，就已经把聚合查询的单元测试给写了。鉴于比较复杂，所以一直没有实现。这周总算完成了这部分代码，心中一块石头落了地。
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原文地址：https://www.cnblogs.com/zgynhqf/p/4270330.html

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