Accessing a count of a child's child properties - entity-framework

Question

I have a three classes District, PostalCode and Premise. District contains a virtual list of postalcodes and the postal code class contains a virtual list of premises, from within the district controller is there any was of calculating the number of premises which are in the district, classes as follows:
public class District
{
[Key]
public int DistrictID { get; set; }
public string Name { get; set; }
public int Households { get; set; }
public int Population { get; set; }
public virtual List<PostalCode> PostalCodes { get; set; }
}
public class PostalCode
{
[Key]
public int PostalCodeID { get; set; }
public string FullPostcode { get; set; }
public bool InUse { get; set; }
public decimal Latitude { get; set; }
public decimal Longitude { get; set; }
public int Easting { get; set; }
public int Northing { get; set; }
public string GridReference { get; set; }
public string Ward { get; set; }
public string Parish { get; set; }
[Display(Name = "Introduced")]
[DataType(DataType.Date)]
[DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
public DateTime Introduced { get; set; }
[Display(Name = "Terminated")]
[DataType(DataType.Date)]
[DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
public DateTime? Terminated { get; set; }
public int Altitude { get; set; }
public string Country { get; set; }
[Display(Name = "Last Updated")]
[DataType(DataType.Date)]
[DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
public DateTime? LastUpdated { get; set; }
public string Quality { get; set; }
public string LSOACode { get; set; }
public bool Processed { get; set; }
[Display(Name = "Last Visited")]
[DataType(DataType.Date)]
[DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
public DateTime? LastVisited { get; set; }
public string SalesRep { get; set; }
public virtual List<Premise> Premises { get; set; }
public int? DistrictID { get; set; }
public virtual District District { get; set; }
}
public class Premise
{
[Key]
public int PremiseID { get; set; }
public string MPRN { get; set; }
public string MeterPointAddress { get; set; }
public string DUoSGroup { get; set; }
public string MeterConfigurationCode { get; set; }
public string MeterPointStatus { get; set; }
public int PostalCodeID { get; set; }
public virtual PostalCode PostalCode { get; set; }
public bool Live { get; set; }
public bool Pending { get; set; }
}
I am able to access the list of postal codes within the view of the district controller by using the following code:
#item.PostalCodes.Count()
I thought that I may have been able to use #item.PostalCodes.All().Premises.Count() or some variation of that but this is not being allowed by the compiler, is there any way that this can be accessing the third level premises class from within the district controller?

Answer 1

You can use Include and 2 foreach loops for this. Take a look at this article
public class Customer
{
public int CustomerID { get; set; }
public string Name { get; set; }
public virtual List<Invoice> Invoices { get; set; }
}
public class Invoice
{
public int InvoiceID { get; set; }
public DateTime Date { get; set; }
public int CustomerID { get; set; }
public virtual Customer Customer { get; set; }
public virtual ICollection<Item> Items { get; set; }
}
public class Item
{
public int ItemID { get; set; }
public string Name { get; set; }
public int InvoiceID { get; set; }
public virtual Invoice Invoice { get; set; }
}
And get data:
using (var context = new MyContext())
{
var list = context.Customers.ToList();
foreach (var customer in list)
{
Console.WriteLine("Customer Name: {0}", customer.Name);
foreach (var customerInvoice in customer.Invoices)
{
var items=customerInvoice.Items.Tolist();
}
}
}

Answer 2

Create a partial class District and add a couple field to this partial class:
public partial class District
{
[NotMapped]
public int PostaCodeCount
[NotMapped]
public int PremissesCount
}
Try this query inside of your controller:
var rowDistricts=db.Districts
.Include(pc=>pc.PostalCodes)
.ThenInclude(pr => pr.Premisses)
.ToList();
var districts= new List<District>();
foreach (var item in rowDistricts)
{
item.PostalCodeCount=item.PostalCodes.Count();
item.PremissesCount=item.Premisses.Count();
item.Premisses=null;
item.PostalCodes=null;
districts.Add(item);
}
return View(districts);