预先不知道有多少列时，在Linq-to-SQL查询中联接多个列

using System;
using System.Linq;
using System.Linq.Dynamic;

public class Program
{
    public static void Main()
    {
        // 假设我们有两个表：Customers和Orders
        // Customers表包含列：CustomerID, CustomerName
        // Orders表包含列：OrderID, CustomerID, OrderDate

        // 假设我们要根据CustomerID和OrderID联接这两个表

        // 创建Linq-to-SQL数据上下文
        var db = new DataContext();

        // 定义联接的列名数组
        var columnNames = new[] { "CustomerID", "OrderID" };

        // 构建动态查询
        var query = db.Customers.Join(db.Orders,
                                      "new(" + string.Join(",", columnNames) + ")",
                                      "new(" + string.Join(",", columnNames) + ")",
                                      "outer");

        // 执行查询
        var result = query.ToList();

        // 输出结果
        foreach (var item in result)
        {
            Console.WriteLine(item.CustomerID + " - " + item.OrderID);
        }
    }
}