如何将这个linq查询转换为lambda？

Question

I have this Query :

return (from r in this.Requests where r.Status == "Authorised" from i in r.Items select i).Sum(i => i.Value);

I tried converting it to lambda as I prefer that now, so I did :

var sum = Requests.Where(x=>x.Status == "Authorised").Select(x=>x.Items).Sum(x=>x.Value); --> and here I got no Value Item, any ideas why?

Answer 1

You need SelectMany instead of Select . Your query is basically equivalent to:

return this.Requests
           .Where(r => r.Status == "Authorised")
           .SelectMany(r => r.Items)
           .Sum(i => i.Value);

Note that your original query would have been clearer on multiple lines too...