Dapper中间映射

Question

在我之前的问题中略微更高级的映射:)

表:

create table [Primary] (
    Id int not null,
    CustomerId int not null,
    CustomerName varchar(60) not null,
    Date datetime default getdate(),
    constraint PK_Primary primary key (Id)
)

create table Secondary(
    PrimaryId int not null,
    Id int not null,
    Date datetime default getdate(),
    constraint PK_Secondary primary key (PrimaryId, Id),
    constraint FK_Secondary_Primary foreign key (PrimaryId) references [Primary] (Id)
)

create table Tertiary(
    PrimaryId int not null,
    SecondaryId int not null,
    Id int not null,
    Date datetime default getdate(),
    constraint PK_Tertiary primary key (PrimaryId, SecondaryId, Id),
    constraint FK_Tertiary_Secondary foreign key (PrimaryId, SecondaryId) references Secondary (PrimaryId, Id)
)

类别:

public class Primary
{
    public int Id { get; set; }
    public Customer Customer { get; set; }
    public DateTime Date { get; set; }
    public List<Secondary> Secondaries { get; set; }
}

public class Secondary
{
    public int Id { get; set; }
    public DateTime Date { get; set; }
    public List<Tertiary> Tertiarys { get; set; }
}

public class Tertiary
{
    public int Id { get; set; }
    public DateTime Date { get; set; }
}

public class Customer
{
    public int Id { get; set; }
    public string Name { get; set; }
}

是否可以使用一个选择来填充它们？像这样的东西:

const string sqlStatement = @"
    select 
        p.Id, p.CustomerId, p.CustomerName, p.Date,
        s.Id, s.Date,
        t.Id, t.Date
    from 
        [Primary] p left join Secondary s on (p.Id = s.PrimaryId)
        left join Tertiary t on (s.PrimaryId = t.PrimaryId and s.Id = t.SecondaryId)
    order by 
        p.Id, s.Id, t.Id
";

然后:

IEnumerable<Primary> primaries = connection.Query<Primary, Customer, Secondary, Tertiary, Primary>(
    sqlStatement,
    ... here comes dragons ...
    );

Edit1 - 我可以使用两个嵌套循环(foreach secondaries - > foreach tertiaries)来执行它,并对每个项执行查询,但只是想知道是否可以使用单个数据库调用来完成.

Edit2 - 也许QueryMultiple方法在这里是合适的,但如果我理解正确,那么我需要多个select语句.在我的实际例子中,select有超过20个条件(在where子句中),其中search参数可以为null,所以我不想重复所有查询中所有语句的所有条件...

Answer 1

Dapper 支持多重映射，文档请参见：http://code.google.com/p/dapper-dot-net/

这是我目前正在进行的项目之一的示例之一：

        var accounts2 = DbConnection.Query<Account, Branch, Application, Account>(
                    "select Accounts.*, SplitAccount = '', Branches.*, SplitBranch = '', Applications.*" +
                    " from Accounts" +
                    "    join Branches" +
                    "       on Accounts.BranchId = Branches.BranchId" +
                    "    join Applications" +
                    "       on Accounts.ApplicationId = Applications.ApplicationId" +
                    " where Accounts.AccountId <> 0",
                    (account, branch, application) =>
                    {
                        account.Branch = branch;
                        account.Application = application;
                        return account;
                    }, splitOn: "SplitAccount, SplitBranch"
                    ).AsQueryable();

技巧是使用 splitOn 选项，将记录集划分为多个对象。

您还可以检查我的问题以查看上述示例的类结构：Dapper Multi-mapping Issue