在使用闭包的LINQ语句中，是否可以在闭包中指定where子句？

Question

Here is the problem I am attempting to solve. I have 3 database tables - Sales, Customer, and Time. One sales record links to exactly one customer record, and one time record. I want to, for the year 1996 only, look at the total sales by region (a customer is tied to a specific region), for the following further divisions: by holidays, non-holidays, weekdays, and weekends. Here is the query I have so far roughly, with what I am trying to add in comments.

var totalSales = 
    from s in sales
    where s.Time.Year = 1996
    group s by s.Customer.Region into g
    select new { Region = g.Key, 
                Holidays = g.Sum(s => s.Total_Amount), // WHERE (s => s.Time.Holiday_flag = true)
                NonHolidays = g.Sum(s => s.Total_Amount), // WHERE (s => s.Time.Holiday_flag = false)
                Weekdays = g.Sum(s => s.Total_Amount), // WHERE (s => s.Time.Weekday_flag = true)
                Weekends = g.Sum(s => s.Total_Amount)}; // WHERE (s => s.Time.Weekday_flag = false)

To do this, I would need to be able to, within each closure, further limit the results. Is this possible? Do I need to restructure the query? I could of course accomplish this by breaking it apart into 4 separate queries, but it would be really nice to do it in one.

Thanks.

Answer 1

Well, you could try this:

Holidays = g.Where(s => s.Time.Holiday_flag).Sum(s => s.Total_Amount),
NonHolidays = g.Where(s => !s.Time.Holiday_flag).Sum(s => s.Total_Amount),
Weekdays = g.Where(s => s.Time.Weekday_flag).Sum(s => s.Total_Amount),
Weekends = g.Where(s => !s.Time.Weekday_flag).Sum(s => s.Total_Amount)

or:

Holidays = g.Sum(s => s.Time.Holiday_flag ? s.Total_Amount : 0),
// etc