Question

我正在尝试使用Dapper执行以下操作（并且失败）。

我的POCO（简化所有代码）是：

    public class Company
    {
        public int CompanyId { get; private set; }
        public string CompanyName { get; private set; }
        public Person CompanyAddress { get; private set; }
        public Person Administrator { get; private set; }
}
    public class Person
    {
        public int PersonId { get; private set; }
        public string FirstName { get; private set; }
        public string LastName { get; private set; }
}

在数据库中，Company表有一个FK for CompanyAddress和Administrator，它映射到Person表中的PersonID PK。根据{{3}}和this我认为以下是我想要这样做的方式：

public static Company Select(IDbConnection connection, int id)
{
    Trap.trap();
    return connection.Query<Company, Person, Person, Company>("select * from Company left join Person address on Company.CompanyAddress = address.PersonId left join Person admin on Company.Administrator = admin.PersonId where Company.CompanyId = @Id",
        (cmpy, addr, admin) => new { PersonId = id }).FirstOrDefault();
}

但是这给了我一个关于“new {PersonId = id}”的编译错误。我错了什么？

Answer 1

您需要提供SplitOn参数来指定下一个表/类的起始位置。您也不应该创建匿名类型，而是使用新范围来初始化Administrator的{{1}}属性：

Company

但是，由于你有两个连接到同一个表，我不确定它是否已经有效。所以我认为你需要所有重复列的别名，如string sql = @"select c.CompanyId,c.CompanyName, c.CompanyAddress, address.PersonId, etc. .... from Company c left join Person address on Company.CompanyAddress = address.PersonId left join Person admin on Company.Administrator = admin.PersonId where Company.CompanyId = @Id"; string splitOn = "PersonId"; // maybe two parameters separated by comma, see comment below the answer return connection.Query<Company, Person, Person, Company>(sql, (Company cmpy, Person addr, Person admin) => { cmpy.Administrator = admin; return cmpy; } ,null,null,true,splitOn) .FirstOrDefault();。但无论如何，这个迁移都会有所帮助。

如何在Dapper中使用多映射？

1 个答案: