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问题： 我正在尝试使用 PetaPoco 加入四个以上的表来填充一个类型为 A 的对象，其中包含五个 B 类型的成员（非常类似于这个问题：https ://stackoverflow.com/a/11275334/296296 ）。根据我的阅读，可以使用以下语法：

var result = db.Query<Investment>(new System.Type[] { typeof(Investment), typeof(Person), typeof(Person), typeof(Person), typeof(Person), typeof(Person) }, null, sql, null).FirstOrDefault();

sql在哪里：

        SELECT Investment.*, p1.*, p2.*, p3.*, p4.*, p5.* FROM Investment
        INNER JOIN People p1 ON Investment.OwnerID = p1.Id
        INNER JOIN People p2 ON Investment.ITOwnerID = p2.Id
        INNER JOIN People p3 ON Investment.InformationOwnerId = p3.Id
        INNER JOIN People p4 ON Investment.MaintenanceLeaderId = p4.Id
        INNER JOIN People p5 ON Investment.MaintenanceLeaderITId = p5.Id
        WHERE (Investment.Id = @0)

但它只是给了我以下错误：

 Can't auto join Person as Investment has more than one property of type Person

任何有同样问题或可以以任何方式提供帮助的人？

背景：

我有以下（简化的）数据库表：

Investment
--------------
Id
Name
OwnerId
ITOwnerId
InformationOwnerId
MaintenanceLeaderId
MaintenanceLeaderITId

People
--------------
Id
Name

我想将这些数据库表映射到的类是：

 Public class Investment {
    public int Id 
    public string Name
    public Person Owner
    public Person ITOwner
    public Person InformationOwner
    public Person MaintenanceLeader
    public Person MaintenanceLeaderIT
 }

 Public class Person {
    public int Id 
    public string Name
 }

为此，我需要为 Investment 类中的每个 Person 类型加入 People 表，并将它们作为 Person 类型的实例映射到相应的属性。

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2 回答 2

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您可能这样做的唯一方法是创建自己的回调（而不是让它回退到当前正在调用的自我发现回调），您可以在其中连接 Investment 对象上的每个 Person 对象。

看看http://www.toptensoftware.com/Articles/115/PetaPoco-Mapping-One-to-Many-and-Many-to-One-Relationships

于 2012-07-11T12:35:16.247 回答
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你为什么不能这样做：

/////用于测试选择的 SQL 代码

DECLARE @People TABLE (Id INT,  Name VARCHAR(50))
        INSERT INTO @People (Id,Name)
            SELECT 1,' John Smith' UNION ALL
            SELECT 2,'Albert Lee' UNION ALL
            SELECT 3,'Christina Wetherbe' UNION ALL
            SELECT 4,'Alice Cany' UNION ALL
            SELECT 5,'Jim Blabery' UNION ALL
            SELECT 6,'Octaviose Mayflower' UNION ALL
            SELECT 7,'Sandra Lee M' UNION ALL
            SELECT 8,'Some test user' UNION ALL
            SELECT 9,'Some test user 2' UNION ALL
            SELECT 10,'Some test user 3' UNION ALL
            SELECT 11,'Some test user 4' 


    DECLARE @Investment TABLE (
                    Id INT,
                    Name VARCHAR(50),
                    OwnerId INT,
                    ITOwnerId  INT,
                    InformationOwnerId INT,
                    MaintenanceLeaderId INT,
                    MaintenanceLeaderITId INT
                )


    INSERT INTO @Investment(Id,Name,OwnerId,ITOwnerId,InformationOwnerId,MaintenanceLeaderId,MaintenanceLeaderITId)
    SELECT 1,'INVESTMENT 1',1,2,1,3,4 UNION ALL
    SELECT 2,'INVESTMENT 2',1,3,2,3,2 UNION ALL
    SELECT 3,'INVESTMENT 3',3,1,3,3,4 UNION ALL
    SELECT 4,'INVESTMENT 4',5,4,4,2,3 UNION ALL
    SELECT 5,'INVESTMENT 5',6,5,5,7,6 UNION ALL
    SELECT 6,'INVESTMENT 6',8,6,6,7,8 UNION ALL
    SELECT 7,'INVESTMENT 7',9,8,7,4,5 UNION ALL
    SELECT 8,'INVESTMENT 8',11,8,8,6,11 UNION ALL
    SELECT 9,'INVESTMENT 9',10,9,9,10,9


    --SELECT * FROM @People
    --SELECT * FROM @Investment

     -- THIS IS YOUR SELECT STATEMENT to be uses in PetaPoco call
    SELECT unpv.Id,unpv.Name, unpv.INVTYPE,unpv.PersonId,p.Name FROM @Investment
    UNPIVOT(PersonId for INVTYPE in    (OwnerId,ITOwnerId,InformationOwnerId,MaintenanceLeaderId,MaintenanceLeaderITId))unpv 
    join @People p on unpv.PersonId = p.Id
    order by INVTYPE, PersonId

然后 C# 代码为

1 - 扩展您的投资 POCO 以增加 2 列，INVTYPE 和 PersonId。只需在相同的命名空间中创建新对象。像这样： 

    public partial class Investment
    {
        [ResultColumn]
        public string INVTYPE { set; get; }
        [ResultColumn]
        public int PersonId { set; get; }
    }

2 - 创建视图类 InvestmentView （您可以使用您的投资类，只需重命名它）

   var myInvestmentView = new InvestmentView
                            {
                              Id = result.Id,
                              Name = result.Name,
                              Owner = new Person{ Id = result.firstOrDefault(o => o.INVTYPE.Equals("OwnerId")).PersonId, Name =  result.firstOrDefault(o=> o.INVTYPE.Equals("OwnerId")).PersonName},
                              ITOwner  = new Person{ Id = result.firstOrDefault(o => o.INVTYPE.Equals("ITOwnerId")).PersonId, Name =  result.firstOrDefault(o=> o.INVTYPE.Equals("ITOwnerId")).PersonName},
                              InformationOwner  = new Person{ Id = result.firstOrDefault(o => o.INVTYPE.Equals("InformationOwnerId")).PersonId, Name =  result.firstOrDefault(o=> o.INVTYPE.Equals("InformationOwnerId")).PersonName},
                              MaintenanceLeader = new Person{ Id = result.firstOrDefault(o => o.INVTYPE.Equals("MaintenanceLeaderId")).PersonId, Name =  result.firstOrDefault(o=> o.INVTYPE.Equals("MaintenanceLeaderId")).PersonName},
                              MaintenanceLeaderIT = new Person{ Id = result.firstOrDefault(o => o.INVTYPE.Equals("MaintenanceLeaderITId")).PersonId, Name =  result.firstOrDefault(o=> o.INVTYPE.Equals("MaintenanceLeaderITId")).PersonName}
                            }

3 - 使用返回列表中的数据填充类

    using (var data = new Database(Config.MainDbConnectionName))
    {
       var result = data.Fetch<Investment,People>(
                        Sql.Builder
                           .Append("SELECT unpv.Id,unpv.Name, unpv.INVTYPE,unpv.PersonId,p.name as PersonName FROM Investment")
                           .Append(" UNPIVOT(PersonId for INVTYPE in    (OwnerId,ITOwnerId,InformationOwnerId,MaintenanceLeaderId,MaintenanceLeaderITId)) unpv")
                           .Append(" JOIN People p on unpv.PersonId = p.Id")
                           .Append(" WHERE (Investment.Id = @0)",InvId)
                           .Append(" ORDER BY INVTYPE, PersonId")
                    );
    }

这样，唯一需要特殊处理的类将是 Investment 类，因为您需要将数据从 InvestmentView 向后处理到 POCO 的平面结构中。

于 2013-03-06T16:12:16.707 回答