使用Dapper映射嵌套对象

CREATE TABLE Users (
    Id INT PRIMARY KEY,
    Name NVARCHAR(100)
);

CREATE TABLE Orders (
    Id INT PRIMARY KEY,
    UserId INT,
    ProductName NVARCHAR(100),
    FOREIGN KEY (UserId) REFERENCES Users(Id)
);

public class User
{
    public int Id { get; set; }
    public string Name { get; set; }
    public List<Order> Orders { get; set; }
}

public class Order
{
    public int Id { get; set; }
    public int UserId { get; set; }
    public string ProductName { get; set; }
}

using System.Collections.Generic;
using System.Data.SqlClient;
using Dapper;

public class UserRepository
{
    private readonly string _connectionString;

    public UserRepository(string connectionString)
    {
        _connectionString = connectionString;
    }

    public User GetUserWithOrders(int userId)
    {
        using (var connection = new SqlConnection(_connectionString))
        {
            connection.Open();

            var query = @"
                SELECT u.Id, u.Name, o.Id AS OrderId, o.ProductName
                FROM Users u
                LEFT JOIN Orders o ON u.Id = o.UserId
                WHERE u.Id = @UserId";

            return connection.Query<User, Order, User>(query, (user, order) =>
            {
                user.Orders ??= new List<Order>();
                user.Orders.Add(order);
                return user;
            }, splitOn: "OrderId", param: new { UserId = userId }).FirstOrDefault();
        }
    }
}