Slapper幫助Dapper實現一對多

Dapper的Query的方法提供了多個泛型重載可以幫助我們實現導航屬性的查詢

1對1

public class Employees4List
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Mobile { get; set; }
    public Department4Employees Department { get; set; }
}
public class Role4Employees
{
    public int Id { get; set; }
    public string Name { get; set; }
}
IEnumerable<Employees4List> GetEmployees()
{
    var sql = $@"
            select #e.[Id],#e.[Name],#e.[Mobile]
            ,#depart.id,#depart.name
            from dbo.T_Eemploye #e
            left join [dbo].[T_Department] #depart on #depart.id = #e.Department
            ";
    using (var conn = GetReadConnection())
    {
        var list = conn.Query<Employees4List, Department4Employees, Employees4List>(sql, (e, d) =>
        {
            e.Department = d;
            return e;
        });
        return list;
    }
}

1對n

但是如果職工類中加入這樣一個屬性呢 ？ public List<Role4Employees> Role { get; set; }

public class Employees4List
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Mobile { get; set; }
    public List<Role4Employees> Role { get; set; }
    public Department4Employees Department { get; set; }
}
public class Role4Employees
{
    public int Id { get; set; }
    public string Name { get; set; }
}
public class Department4Employees
{
    public int Id { get; set; }
    public string Name { get; set; }
}

之前看到過這樣一個方式，但是它是不能像我們想象的那樣工作，這里如果一個Eemploye有多個角色，那就和原始的sql語句一樣，他會產生重復的記錄

IEnumerable<Employees4List> GetEmployees()
{
    var sql = $@"
    select #e.[Id],#e.[Name],#e.[Mobile]
    ,#depart.id,#depart.name
    ,#role.id,#role.name
    from dbo.T_Eemploye #e
    left join [dbo].[T_Department] #depart on #depart.id = #e.Department
    left join [dbo].[T_Role]       #role   on #role.value & #e.role = #role.value
    ";
    using (var conn = GetReadConnection())
    {
        var list = conn.Query<Employees4List, Department4Employees, Role4Employees, Employees4List>(sql,(e, d, r) =>
        {
            e.Department = d;
            e.Role.Add(r);
            return e;
        });
        return list;
    }
}

正確的方式是使用Slapper.Automapper，這個包需要獨立安裝

IEnumerable<Employees4List> GetEmployees()
{
    var sql = $@"
        select #e.[Id],#e.[Name],#e.[Mobile]
        ,#role.id Role_Id,#role.name Role_Name
        ,#depart.id Department_Id,#depart.name Department_Name
        from dbo.T_Eemploye #e
        left join [dbo].[T_Role]       #role   on #role.value & #e.role = #role.value
        left join [dbo].[T_Department] #depart on #depart.id = #e.Department
    ";
    using (var conn = GetReadConnection())
    {
        var dynamic = conn.Query<dynamic>(sql);

        Slapper.AutoMapper.Configuration.AddIdentifiers(typeof(Employees4List), new List<string> { "Id" });
        Slapper.AutoMapper.Configuration.AddIdentifiers(typeof(Role4Employees), new List<string> { "Id" });
        Slapper.AutoMapper.Configuration.AddIdentifier(typeof(Department4Employees), "Id");

        var list = (Slapper.AutoMapper.MapDynamic<Employees4List>(dynamic) as IEnumerable<Employees4List>).ToList();

        return list;
    }
}

通過AddIdentifier和AddIdentifier來識別外鍵是1對1還是1對n，需要注意的是這里需要對字段取別名，怎么取呢？

新的名稱以在c#類中字段名稱+下划線+導航類的字段名稱

比如說Employees4List中有一個屬性Role要做1對n查詢，通過AddIdentifiers方法指明需要轉換的類型名稱和主鍵名稱，其次在sql語句中通過

Role_Id和Role_Name來取別名，下划線前面的Role來自Employees4List的 Role屬性，下划線后面的 Id 和 Name來自 Role4Employees