sum values in a child entity - linq

Question

I have an entity with a parent class and two child classes, like this:
Tax Report --> Parcel --> Tax Collector
Tax Report contains a collection of Parcel, and Parcel contains a collection of Tax Collector.
My Tax Report object has 2 Parcel objects associated with it, and each Parcel object has 2 Tax Collector objects associated with it. The Tax Collector object has a property called Taxes Due that I am interested in. Here is an example of the data:
TaxReport: 1
Parcel: 0001
Tax Collector: Dallas County, $100 in taxes due
Tax Collector: Collin County, $50 in taxes due
Parcel: 0002
Tax Collector: Collin County, $1000 in taxes due
Tax Collector: City of Irving, $100 in taxes due
I want to query my objects to sum the taxes due for all parcels, grouped by Tax Collector. Here is what I want my result to look like:
Dallas County, $100
Collin County, $1050
City of Irving, $100
I have tried something along these lines:
var taxsummary = from tr in taxreport.Parcel.Select(y=>y.TaxCollector).Select(n=>n.TaxesDue).Sum()
But I haven't had any luck. My results are always projected as a multi-level collection with Taxes Due below each Parcel, not grouped by Tax Collector. Any ideas?
Thanks,
Brad

Answer 1

This does the trick:
var grouped = from parcel in taxReport.Parcels
from taxCollector in parcel.TaxCollectors
group taxCollector by new
{
Name = taxCollector.Name // Or whatever makes it Unique...
};
foreach(var collectorGroup in grouped)
{
Console.WriteLine(collectorGroup.Key.Name + " : " + collectorGroup .Sum(p => p.TaxesDue));
}
If you want something like a Dictionary you can do this:
var grouped = (from parcel in taxReport.Parcels
from taxCollector in parcel.TaxCollectors
group taxCollector by new
{
Name = taxCollector.Name
}
into groupedCollectors
select new
{
Name = groupedCollectors.Key.Name,
TaxesDue = groupedCollectors.Sum(p => p.TaxesDue)
})
.ToDictionary(p =>p.Name, p => p.TaxesDue);