Filter EF Core Navigation property on GraphQL HotChocolate

Question

I am using HotChocolate (11.2.2) with EF Core and want to filter a sub property. According to the GraphQL docu this should be possible by using the filter keyword on the navigation property but HotChocolate just fails.

My schema:

type A {
    Name: string,
    RefTo: [B]
}
type B {
    TypeName: string,
    Value: int
}

This is backed by EF and I provide an IQueryable<A> to HotChocolate.

[UsePaging]
[UseProjection]
[UseFiltering]
[UseSorting]
public IQueryable<A> GetAs([Service] Context db) => db.As.AsSingleQuery().AsNoTrackingWithIdentityResolution();

Now I want to include only those B s where the TypeName is equal to "ExampleType" like this:

query {
   As {
      Name,
      RefTo(where: { TypeName: { eq: "ExampleType" } })
      {
          TypeName,
          Value
      }
   }
}

But HotChcolate does not seem to understand this and says:

Unknown argument "where" on field "A.RefTo".validation

Is it possible to filter Navigation Properties with an EF Core model?

Answer 1

You would have to add filtering to RefTo too

    [UseFiltering] 
    public ICollection<A> RefTo {get; set;}

Answer 2

If you want to apply UseFiltering , UseSorting , etc. to all fields with result type ICollection you can use a TypeInterceptor :

using System;
using System.Collections.Generic;
using HotChocolate.Configuration;
using HotChocolate.Types;
using HotChocolate.Types.Descriptors;
using HotChocolate.Types.Descriptors.Definitions;

namespace MyApp
{
    public class FilterCollectionTypeInterceptor : TypeInterceptor
    {
        private static bool IsCollectionType(Type t)
            => t.IsGenericType && t.GetGenericTypeDefinition() == typeof(ICollection<>);

        public override void OnBeforeRegisterDependencies(ITypeDiscoveryContext discoveryContext, DefinitionBase? definition,
            IDictionary<string, object?> contextData)
        {
            if (definition is not ObjectTypeDefinition objectTypeDefinition) return;
            
            for (var i = 0; i < objectTypeDefinition.Fields.Count; i++)
            {
                var field = objectTypeDefinition.Fields[i];
                if (field.ResultType is null || !IsCollectionType(field.ResultType)) continue;
                
                var descriptor = field.ToDescriptor(discoveryContext.DescriptorContext)
                    .UseFiltering()
                    .UseSorting();
                objectTypeDefinition.Fields[i] = descriptor.ToDefinition();
            }
        }
    }
}

See my gist here: https://gist.github.com/zliebersbach/b7db2b2fcede98f220f55aa92276ad6e#file-filtercollectiontypeinterceptor-cs