集合中项目的总和

问题描述

使用LINQ to SQL，我有一个Order类，其中包含OrderDetails的集合.订单明细具有一个名为LineTotal的属性，该属性获得Qnty x ItemPrice.

Using LINQ to SQL, I have an Order class with a collection of OrderDetails. The Order Details has a property called LineTotal which gets Qnty x ItemPrice.

我知道如何对数据库执行新的LINQ查询以查找订单总额，但是由于我已经从数据库中获得了OrderDetails的集合，因此有一种简单的方法可以直接从集合中返回LineTotal的总和?

I know how to do a new LINQ query of the database to find the order total, but as I already have the collection of OrderDetails from the DB, is there a simple method to return the sum of the LineTotal directly from the collection?

我想将订单总计添加为我的Order类的属性.我想我可以遍历集合并为每个Order.OrderDetail用a计算总和，但是我猜有更好的方法.

I'd like to add the order total as a property of my Order class. I imagine I could loop through the collection and calculate the sum with a for each Order.OrderDetail, but I'm guessing there is a better way.

推荐答案

您可以对对象执行LINQ，并使用LINQ计算总数:

You can do LINQ to Objects and the use LINQ to calculate the totals:

decimal sumLineTotal = (from od in orderdetailscollection
select od.LineTotal).Sum();

您还可以使用lambda-expressions来执行此操作，这有点干净".

You can also use lambda-expressions to do this, which is a bit "cleaner".

decimal sumLineTotal = orderdetailscollection.Sum(od => od.LineTotal);

然后，您可以根据需要将其连接到Order类:

You can then hook this up to your Order-class like this if you want:

Public Partial Class Order {
  ...
  Public Decimal LineTotal {
    get {
      return orderdetailscollection.Sum(od => od.LineTotal);
    }
  }
}

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