使用LINQ从列表中的列表中进行选择

问题描述

嗨！

我想把头缠在LINQ上，但是我发现自己在这里苦苦挣扎.我有几个非常简单的课程:

Hi!

I''m trying to wrap my head around LINQ, but I find myself struggling here. I have a couple of very simple classes:

class Order
    {
        public string AccountNumber;
        public string AccountName;
        public List<OrderLine> OrderLines = new List<OrderLine>();
        public DateTime StartDate;
        public DateTime EndDate;
    }

    class OrderLine
    {
        public string Description;
        public string ProductCode;
        public double Duration;
        public int Quantity;
    }

在运行时，我用Orders实例填充了一个名为customerOrders的新List对象，该对象又具有多个OrderLine实例.现在，我想做的是选择在整个customerOrder对象中使用的独特ProductCode.我已经尝试了一下，并尝试了要塞，这是到目前为止我要提出的内容:

At run-time, I populate a new List object called customerOrders with instances of Orders, which again have multiple instances of OrderLine. Now, what I would like to do is to select the distinct ProductCode used in the entire customerOrder object. I have tried back and fort abit, and this is what I''ve come up with so far:

var c = from d in CustomerOrders select d.OrderLines.ToList();
IEnumerable<string> b = from q in (c as List<OrderLine>) select q.ProductCode;

第一行很好，但是下一行会导致异常，因为c为null.
我什至没有尝试从列表中查找不同的值:)

帮助和提示大加赞赏！

/Geir Rune

The first line is fine, but the next one causes an exception becase c is null.
I didn''t even get to trying to find the distinct values from the list :)

Help and tips much appreciated!

/Geir Rune

推荐答案

var orders = new List<Order>();
var distinctOrderLines = orders.SelectMany(order => order.OrderLines).Distinct();

这篇关于使用LINQ从列表中的列表中进行选择的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！