Include nested entity details but don't group by then when grouping by other fields - json

Question

I working with Database first C# MVC, EF6, LINQ and JSon to try and pass data to both Highcharts and Google Maps for some of my reporting.
If I could add an image I would show you the relevant portion of my model, but sadly I need more reputation to do that...
The portion of the Entity Model I'm concentrating on right now is based on a central Docket that contains a BuildingCode as part of a one-to-many relationship to a building with and address and further relationship to the buildings polygons (for mapping). Dockets are also classified by one or more DocketTypes and thus there is a many-to-many relationship between Dockets and DocketTypes, which is not directly exposed to through the EF.
As an example a Docket which represents an investigation, could be related to the theft of a mobile phone in building A located on Campus X, not only was the cellphone stolen but the assailant also assaulted the victim in order to steal the mobile phone. So there are 2 DocketTypes here 1. Theft of mobile phone and 2. assault. Note: this is fictitious and for illustration purposes only .
One of my fundamental reports requires that I count how many docketTypes affect each building and each campus in a given period. When I display this I also need to show what the DocketTypes are.
I have no end of nightmare trying to find a way to get this right, I keep running into circular reference errors and needing to use explicit conversions when trying to model the data with LINQ so that I can pass a single nested object through JSON to the client side where displaying will occur.
In the below code I am told I need an Explicit conversion:
Cannot implicitly convert type 'Campus_Investigator.ViewModels.DocketTypeViewModel' to 'System.Collections.Generic.IEnumerable<Campus_Investigator.ViewModels.DocketTypeViewModel>'. An explicit conversion exists (are you missing a cast?)
var currentDocketQuery = from d in db.Dockets
from dt in d.DocketTypes
from bp in d.BuildingDetail.BuildingPolygons
where d.OccurrenceStartDate >= datetime && d.BuildingDetail.CampusName == Campus
select new CampusBuildingDocketTypeViewModel()
{
BuildingCode = d.BuildingDetail.BuildingCode,
BuildingName = d.BuildingDetail.BuildingName,
//BuildingPolygons = d.BuildingDetail.BuildingPolygons,
DocketTypes = new DocketTypeViewModel()
{
Category = dt.Category,
SubCategory = dt.SubCategory,
ShortDescription = dt.ShortDescription
}
};
I appreciate any ideas on how I can explicitly convert this or is that a better method I can use and avoid the circular reference error?

Answer 1

You included some redundant part in your query (which performs some inner join). The from bp in d.BuildingDetail.BuildingPolygons is joined in but then is not shown in the result. So it totally does not make sense. There may be duplicated elements in the result due to that. The from dt in d.DocketTypes is wrong joined in, although you need it in the result but because the DocketTypes is output per d in db.Dockets, so it's just simply queried like this:
var currentDocketQuery = from d in db.Dockets
where d.OccurrenceStartDate >= datetime && d.BuildingDetail.CampusName == Campus
select new CampusBuildingDocketTypeViewModel()
{
BuildingCode = d.BuildingDetail.BuildingCode,
BuildingName = d.BuildingDetail.BuildingName,
//BuildingPolygons = d.BuildingDetail.BuildingPolygons,
DocketTypes = d.DocketTypes
};
In fact I can see the commented line //BuildingPolygons = d.BuildingDetail.BuildingPolygons, so if you want to include that, it should also work.
If the DocketTypes has different type of d.DocketTypes, then you need a simple projection like this:
var currentDocketQuery = from d in db.Dockets
where d.OccurrenceStartDate >= datetime && d.BuildingDetail.CampusName == Campus
select new CampusBuildingDocketTypeViewModel()
{
BuildingCode = d.BuildingDetail.BuildingCode,
BuildingName = d.BuildingDetail.BuildingName,
//BuildingPolygons = d.BuildingDetail.BuildingPolygons,
DocketTypes = d.DocketTypes.Select(e => new DocketTypeViewModel()
{
Category = e.Category,
SubCategory = e.SubCategory,
ShortDescription = e.ShortDescription
})
};

Answer 2

I managed to solve this one by using the below. The major hassle with this is the circular referencing that exists in the model. When JSON serializes these, everything falls apart so it takes a lot of transforming to make sure that I only extract what I need. In this case grouped campus and building data (below includes the polygons which where only half commented out in the above) and then the include the detail of the DocketTypes that occurred at each building.
var datetime = DateTime.Now.AddDays(-30);
var campusDocket = from d in db.Dockets
where d.OccurrenceStartDate >= datetime && d.BuildingDetail.CampusName == Campus
group d by new { d.BuildingDetail.CampusName, d.BuildingDetail.BuildingCode, d.BuildingDetail.BuildingName } into groupdata
select new CampusBuildingDocketTypeViewModel
{
BuildingCode = groupdata.Key.BuildingCode,
BuildingName = groupdata.Key.BuildingName,
CampusName = groupdata.Key.CampusName,
Count = groupdata.Count(),
BuildingPolygons = from bp in db.BuildingPolygons
where bp.BuildingCode == groupdata.Key.BuildingCode
select new BuildingPolygonViewModel
{
Accuracy = bp.Accuracy,
BuildingCode = bp.BuildingCode,
PolygonOrder = bp.PolygonOrder,
Latitude = bp.Latitude,
Longitude = bp.Longitude
},
DocketTypes = from doc in db.Dockets
from dt in doc.DocketTypes
where doc.OccurrenceStartDate >= datetime && doc.BuildingCode == groupdata.Key.BuildingCode
select new DocketTypeViewModel
{
Category = dt.Category,
SubCategory = dt.SubCategory,
ShortDescription = dt.ShortDescription
}
};
The Answer again is ViewModels. I'm finding ViewModels seem to solve a lot of problems...