C# Entity Framework Core: how do I get the relationship of the bill to the vendor without including the vendor's list of bills?

Question

I am trying to exclude a relationship from a database query using linq in Entity Framework Core.

I have a database where I have a table of Bills and a table of Vendors.

• Each Bill has 1 Vendor
• Each Vendor has many Bills

I want to exclude the List<Bill> from the Vendor while maintaining the Vendor information for the Bill I am querying. So I can gather Vendor information from that specific Bill. I currently have the relation as below.

foundBills = db_context.Bills.Include(v => v.Vendor).Where(searchLambda).ToList();

Is there a .Exclude or .Intersect or something that I am missing to exclude the circular relationship? It is using way too much memory.

Answer 1

If you configured your Bill and Vendor Model classes correctly for "One to Many" relationship, they should look like this:

public class Vendor
{
    // ... other properties

    public Bill Bill { get; set; }
}

public class Bill
{
    // ... other properties

    public ICollection<Vendor> Vendors { get; set; }
}

With this logic, there shouldn't be any circular dependency, because this is how it works.

Later you can use Include or not, but if you want to not have a Bill information in your Vendor for the final output then create separate models for Vendor and Bill:

public class BillOutput
{
    public List<VendorOutput> Vendors { get; set; }
}


public class VendorOutput
{
    // ... other properties
}

and later:

var finalOutput = db_context.Bills.Include(v => v.Vendor).Where(searchLambda).
                      Select(items => new BillOutput
                      {
                          Vendors = items.Select(item => new VendorOutput
                          {
                              // here you don't have the Bill Information
                          }
                      } )
                     .ToList();