如何在汇总另一个房产时汇总一个房产？

Question

我有一张发票清单，每个记录包含一个客户ID和金额。其目的是为每个客户（每个客户可能有多个发票）生成一个付款清单，并将相关发票金额总计为一个总额。

生成不同发票清单（关于客户ID）为very easy。事情是，我只有第一张发票金额的价值，而不是金额。

List<Payment> distinct = invoices 
    .GroupBy(invoice => invoice.CustomerId) 
    .Select(group => group.First()) 
    .Select(invoice => new Payment 
    { 
    CustomerId = invoice.CustomerId, 
    Total = invoice.Amount 
    }).ToList(); 

是否有一个流畅的LINQ-FU为或者我需要去的foreach我的名单上？

Answer 1

如果你有这样的事情

Invoice[] invoices = new Invoice[3]; 

invoices[0] = new Invoice { Id = 1, Amount = 100 }; 
invoices[1] = new Invoice { Id = 1, Amount = 150 }; 
invoices[2] = new Invoice { Id = 2, Amount = 300 }; 

为基于jmelosegui的答案

var results = from i in invoices 
       group i by i.Id into g 
       select new { Id = g.Key, TotalAmount = g.Sum(i => i.Amount)}; 

Answer 2

然后你可以有你的目标：

List<Payment> distinct = invoices 
    .GroupBy(c => c.CustomerId) 
    .Select(c => new Payment 
    { 
    CustomerId = c.Key, 
    Total = c.Sum(x => x.Amount) 
    }).ToList();