使用C#和导航属性的查询实体框架

using System;
using System.Linq;

// 定义实体类
public class Order
{
    public int OrderId { get; set; }
    public string OrderNumber { get; set; }
    public int CustomerId { get; set; }
    public Customer Customer { get; set; }
}

public class Customer
{
    public int CustomerId { get; set; }
    public string CustomerName { get; set; }
    public ICollection<Order> Orders { get; set; }
}

// 创建DbContext
public class MyDbContext : DbContext
{
    public DbSet<Order> Orders { get; set; }
    public DbSet<Customer> Customers { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer("连接字符串");
    }
}

// 查询数据
public class Program
{
    public static void Main(string[] args)
    {
        using (var context = new MyDbContext())
        {
            var orders = context.Orders
                .Include(o => o.Customer) // 使用导航属性关联查询
                .Where(o => o.Customer.CustomerName == "张三")
                .ToList();

            foreach (var order in orders)
            {
                Console.WriteLine($"订单号：{order.OrderNumber}，客户名：{order.Customer.CustomerName}");
            }
        }
    }
}