在列表C#中使用相同参数连接条目

Question

假设我有以下列表

List<Invoice> InvoiceList

[0]
   AdvertiserCustomerID = "Generic Brand"
   GrossAmount = 1452
[1]
   AdvertiserCustomerID = "Generic Brand"
   GrossAmount = 4325
[2]
   AdvertiserCustomerID = "Generic Brand"
   GrossAmount = 2
[3]
   AdvertiserCustomerID = "Generic Brand 2"
   GrossAmount = 9211

将具有相同AdvertiserCustomerID的品牌组合到一个条目中的最简单方法是什么,并计算GrossAmount的总和？所以最终的列表看起来像这样:

List<Invoice> InvoiceList

[0]
   AdvertiserCustomerID = "Generic Brand"
   GrossAmount = 5779
[1]
   AdvertiserCustomerID = "Generic Brand 2"
   GrossAmount = 9211

我通过创建一个新列表并使用FindIndex检查AdvertiserCustomerID来实现这一点,但我想知道是否有更简单的方法来执行此操作.

谢谢.

Answer 1

var result = InvoiceList
     .GroupBy(m => m.AdvertiserCustomerId)
     .Select(group => new Invoice {
                AdvertiserCustomerID = group.Key,
                GrossAmount = group.Sum(g => g.GrossAmount)
                }
     );

(在你的例子中,你没有乘,你总和)

这会给你一个IEnumerable<Invoice>,你可以.ToList()在最后添加一个枚举.