使用LINQ的总和属性

Question

DealsThisMonthOpen = deals.Where(deal => deal.DateCreated.Month == date.Month && deal.DealStatus == "Open").Count(), 
DealsThisMonthLost = deals.Where(deal => deal.DateCreated.Month == date.Month && deal.DealStatus == "Lost").Count(), 
DealsThisMonthWon = deals.Where(deal => deal.DateCreated.Month == date.Month && deal.DealStatus == "Won").Count(), 
DealsThisMonth = DealsThisMonthOpen + DealsThisMonthLost + DealsThisMonthWon; 

最后一行语法不正确。是否有可能这样做，否则我将不得不为此属性编写查询来计算总和？

感谢

Answer 1

顺便说一句，Count()还支持predicate说法： http://msdn.microsoft.com/en-us/library/bb535181.aspx

，因此您可以：

var a = deals.Count(deal => deal.DateCreated.Month == date.Month && deal.DealStatus == "Open"), 
var b = deals.Count(deal => deal.DateCreated.Month == date.Month && deal.DealStatus == "Lost"), 
var c = deals.Count(deal => deal.DateCreated.Month == date.Month && deal.DealStatus == "Won"), 

new foobar 
{ 
    DealsThisMonthOpen = a, 
    DealsThisMonthLost = b, 
    DealsThisMonthWon = c, 
    DealsThisMonth = a + b + c 
}; 

Answer 2

你有没有考虑的扩展方法？您提供总和功能的地方。

Answer 3

也许我失去了一些东西，但一定要努力。

Count(的）方法返回一个int所以DealsThisMonthOpen，DealsThisMonthLost，和DealsThisMonthWon都是整数值。 DealsThisMonth只是这三个整数值的总和。

你也可以把它干净了一点（除非你需要三个不同值别的东西以后：

var dealsThisMonth = deals 
    .Count(d => d.DateCreated.Month == date.Month 
     && (new string[] { "Open", "Lost", "Won" }).Contains(d.DealStatus));