创建多个连接查询 - Dapper

Question

recently i'm working on an application and my instructor asked me to use Dapper as ORM. This is the first time to work on it. I want to create a join query for 3 tables and store the value in custom object.

Here are the tables:

public class Customer
{
public int id { get; set; }
public string fname { get; set; }
public string lname { get; set; }
public List<Orders> Order { get; set; }
}


public class Orders
{
public int id { get; set; }
public string code{ get; set; }
public string name { get; set; }
public  Customer Customer { get; set; }
public  Product Product  { get; set; }
}



public class Product
{
public int id { get; set; }
public string name { get; set; }
public string price { get; set; }
public  List<Orders> Order { get; set; }
}

This DTO Class:

public class CustomDTO
{
public string CustomerName { get; set; }
public string OrderName { get; set; }
public string ProductName { get; set; }
}

I want to store result executed from the dapper join query into CustomDTO

Answer 1

As has been pointed out, you really need to supply more info in your post so people don't have to assume too much. From what you've said, one possible approach is this:

using (var connection = new SqlConnection("YOUR_CONNECTION_STRING"))
{
    connection.Open();

    string cmdTxt = @"SELECT o.name, c.name, p.name
        FROM Orders o
        INNER JOIN Customers c ON o.customerId = c.Id 
        INNER JOIN Products p ON o.productId = p.Id;";

    var results = await connection.QueryAsync<CustomDTO>(cmdTxt);

    if(results.Any()) {
        //do something with the list of `CustomDTO`
    }

    connection.Close();
}

Note: I'm assuming your Orders table has the relevant foreign keys.