C# Linq to SQL .Sum() without group ... into
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/641682/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Linq to SQL .Sum() without group ... into
提问by roman m
I have something like this:
我有这样的事情：
var itemsInCart = from o in db.OrderLineItems
where o.OrderId == currentOrder.OrderId
select new { o.OrderLineItemId, ..., ..., o.WishListItem.Price}
is there any way to do a
有没有办法做一个
itemsCart.Sum() //not sure what to pass into the function
to get the sum of o.WishListItem.Price or do i have to get another iQueryable< T> from the database with group ... into?
获得 o.WishListItem.Price 的总和还是我必须从数据库中获取另一个 iQueryable< T> 与组...进入？
采纳答案by CMS
What about:
关于什么：
itemsInCart.AsEnumerable().Sum(o=>o.Price);
AsEnumerablemakes the difference, this query will execute locally (Linq To Objects).
AsEnumerable有所不同，此查询将在本地执行（Linq To Objects）。
回答by eglasius
you can:
你可以：
itemsCart.Select(c=>c.Price).Sum();
itemsCart.Select(c=>c.Price).Sum();
To hit the db only once do:
只击中数据库一次，请执行以下操作：
var itemsInCart = (from o in db.OrderLineItems
where o.OrderId == currentOrder.OrderId
select new { o.OrderLineItemId, ..., ..., o.WishListItem.Price}
).ToList();
var sum = itemsCart.Select(c=>c.Price).Sum();
The extra round-trip saved is worth it :)
节省的额外往返是值得的:)
回答by Jonathan Parker
Try:
尝试：
itemsCard.ToList().Select(c=>c.Price).Sum();
Actually this would perform better:
实际上这会表现得更好：
var itemsInCart = from o in db.OrderLineItems
where o.OrderId == currentOrder.OrderId
select new { o.WishListItem.Price };
var sum = itemsCard.ToList().Select(c=>c.Price).Sum();
Because you'll only be retrieving one column from the database.
因为您只会从数据库中检索一列。
回答by Dirceu
Try this:
尝试这个：
var itemsInCart = from o in db.OrderLineItems
where o.OrderId == currentOrder.OrderId
select o.WishListItem.Price;
return Convert.ToDecimal(itemsInCart.Sum());
I think it's more simple!
我觉得更简单！
回答by Trisped
I know this is an old question but why can't you do it like:
我知道这是一个老问题，但你为什么不能这样做：
db.OrderLineItems.Where(o => o.OrderId == currentOrder.OrderId).Sum(o => o.WishListItem.Price);
I am not sure how to do this using query expressions.
我不确定如何使用查询表达式来做到这一点。
