我如何獲得多映射在Dapper中工作？

Question

我正在試圖用Dapper（和失敗）做以下事情。

我的波蘇斯（簡化所有代碼）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; } 
} 

在公司表有一個公司地址FK它映射，將personId PK Person表中的數據庫和管理員。基於this和this我認爲follwoing是我要如何做到這一點：

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，這給了我一個編譯錯誤的「新{PERSONID = ID}」。我錯了什麼？

Answer 1

您需要提供SplitOn參數來指定下一個表/類的起始位置。你也應該不是創建一個匿名類型，但使用新的範圍，以初始化的Company的Administrator屬性：

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(); 

不過，我不知道，因爲你有兩個連接到同一個表的作品了。所以我認爲你需要所有重複列的別名，如PersonId。但是這個遷移無論如何都有幫助。