求助：如何将嵌套for-each循环转换为LINQ JOIN实现

• 请提供你原始的for-each循环代码以及已编写的LINQ半成品代码，这样才能针对性地帮你完成剩余逻辑的补全。
• 这里给一个基础的foreach转LINQ JOIN的示例供参考：
  原始foreach循环：

  List<Order> orders = GetOrders();
  List<Customer> customers = GetCustomers();
  List<OrderCustomerDto> combinedList = new List<OrderCustomerDto>();
  
  foreach (var order in orders)
  {
      foreach (var customer in customers)
      {
          if (order.CustomerId == customer.Id)
          {
              combinedList.Add(new OrderCustomerDto 
              { 
                  OrderNumber = order.Number, 
                  CustomerName = customer.Name 
              });
          }
      }
  }
  

  对应的LINQ JOIN实现：

  var combinedList = from order in orders
                     join customer in customers on order.CustomerId equals customer.Id
                     select new OrderCustomerDto 
                     { 
                         OrderNumber = order.Number, 
                         CustomerName = customer.Name 
                     };
  

内容的提问来源于stack exchange，提问作者LonelySemiColon