Querying into a complex object with Dapper

问题

I have a Customer class with the following properties:

public int Id { get; set; }
public string Name { get; set; }
public int AddressId { get; set; }
public Address Address { get; set; }

My goal is to write a Dapper query that will use an Inner Join to populate the entire Address property within each Customer that is returned.

Here is what I have and it is working but I am wondering if this is the cleanest/simplest way to do it:

StringBuilder sql = new StringBuilder();
using (var conn = GetOpenConnection())
{
    sql.AppendLine("SELECT c.Id, c.Name, c.AddressId, a.Address1, a.Address2, a.City, a.State, a.ZipCode ");
    sql.AppendLine("FROM Customer c ");
    sql.AppendLine("INNER JOIN Address a ON c.AddressId = a.Id ");

    return conn.Query<Customer, Address, Customer>(
        sql.ToString(),
        (customer, address) => {
            customer.Address= address;
            return userRole;
        },
        splitOn: "AddressId"
    ).ToList();
}

I have some concern about adding another property such as:

public Contact Contact { get; set; }

I am not sure how I would switch the syntax above to populate both Address and Contact.

回答1:

I have coded using Dapper version 1.40 and I have written queries like the way below, I haven't got any issues to populate mote more than one object, but I have faced a limit of 8 different classes those I can map in a query.

    public class Customer {
        public int Id { get; set; }
        public string Name { get; set; }
        public int AddressId { get; set; }  
        public int ContactId { get; set; }
        public Address Address { get; set; }
        public Contact Contact { get; set; }
    }

    public class Address {
      public int Id { get; set; }
      public string Address1 {get;set;}
      public string Address2 {get;set;}
      public string City {get;set;}
      public string State {get;set;}
      public int ZipCode {get;set;}
      public IEnumerable<Customer> Customer {get;set;}
    }

    public class Contact {
        public int Id { get; set; }
        public string Name { get; set; }
        public IEnumerable<Customer> Customer {get;set;}
    }

    using (var conn = GetOpenConnection())
    {
        var query = _contextDapper
            .Query<Customer, Address, Contact, Customer>($@"
                SELECT c.Id, c.Name, 
                    c.AddressId, a.Id, a.Address1, a.Address2, a.City, a.State, a.ZipCode,
                    c.ContactId, ct.Id, ct.Name
                FROM Customer c
                INNER JOIN Address a ON a.Id = c.AddressId
                INNER JOIN Contact ct ON ct.Id = c.ContactId", 
                (c, a, ct) =>
                {
                    c.LogType = a;
                    c.Contact = ct;
                    return c; 
                }, splitOn: "AddressId, ContactId")
            .AsQueryable();

        return query.ToList();          
    }

回答2:

Take a look in my example with a big query, note that Each Query line It's a different object.

public List<Appointment> GetList(int id)
{
    List<Appointment> ret;
    using (var db = new SqlConnection(connstring))
    {
        const string sql = @"SELECT AP.[Id], AP.Diagnostics, AP.Sintomns, AP.Prescription, AP.DoctorReport, AP.AddressId,
        AD.Id, AD.Street, AD.City, AD.State, AD.Country, AD.ZIP, Ad.Complement,
        D.Id, D.Bio, d.CRMNumber, D.CRMNumber, D.CRMState,
        P.Id,
        S.Id, S.Name,
        MR.Id, MR.Alergies, MR.BloodType, MR.DtRegister, Mr.HealthyProblems, MR.HealthyProblems, MR.Height, MR.MedicalInsuranceNumber, MR.MedicalInsuranceUserName, MR.Medications, MR.Weight,
        MI.Id, MI.Name
        from Appointment AP
        inner join [Address] AD on AD.Id = AP.AddressId
        inner join Doctor D on D.Id = AP.DoctorId
        inner join Patient P on P.Id = AP.PatientId
        left join Speciality S on S.Id = D.IDEspeciality
        left join MedicalRecord MR on MR.Id = P.MedicalRecordId
        left join MedicalInsurance MI on MI.Id = MR.MedicalInsuranceId
        where AP.Id = @Id
        order by AP.Id desc";

        ret = db.Query<Appointment, Address, Doctor, Patient, Speciality, MedicalRecord, MedicalInsurance, Appointment>(sql,
            (appointment, address, doctor, patient, speciality, medicalrecord, medicalinsurance) =>
            {
                appointment.Address = address;
                appointment.Doctor = doctor;
                appointment.Patient = patient;
                appointment.Doctor.Speciality = speciality;
                appointment.Patient.MedicalRecord = medicalrecord;
                appointment.Patient.MedicalRecord.MedicalInsurance = medicalinsurance;
                return appointment;
            }, new { Id = id }, splitOn: "Id, Id, Id, Id, Id, Id").ToList();
    }
    return ret;
}

来源：https://stackoverflow.com/questions/44980945/querying-into-a-complex-object-with-dapper