Add relation resolver using ExtendObjectType

[danrot]

Hey there 👋 I am just wondering if the documentation at https://chillicream.com/docs/hotchocolate/api-reference/object-type/ is correct. I have a Query class that returns a list of Employees:

// Removed

The Employee class has a one-to-many relationship to the Absence, which should be exposed via GraphQL as well. I was wondering what’s the easiest possible way to do that. The way I’ve understood it, would be to introduce an object type extension using “Pure Code-First” as mentioned in the link above, so that’s what I’ve came up with:

// Removed

My first guess was that I should be able to introduce that GetAbsences function in the Query class as well, and the Parent Attribute would automatically recognize when to use that function, but that does not seem to work, so I switched to the approach with the ExtendObjectType attribute. I also registered that class in the Startup.cs file of ASP.NET:

// Removed

But when I try to query absences from the employees now, I always get an empty list, and there are no logs indicating that a database request to that table was done. A RTFM with a link would be totally fine, but I couldn’t find any V11 documentation covering this in more detail than the one above 😕

[gojanpaolo]

@danrot Can you create a project that reproduces the issue?

I tried running the code you provided but it's working fine.

See working sample project here: https://github.com/gojanpaolo/hotchocolate-3178

Runnning the following query:

query {
  employee(id: 1) {
    absences {
      id
    }
  }
}

... returns the following response

{
  "data": {
    "employee": {
      "absences": [
        {
          "id": 1
        }
      ]
    }
  }
}

[gojanpaolo]

@michaelstaib Yes,
@danrot I recommend going over the graphql-workshop if you haven't done so already. IMO the workshop is a great resource to start learning HC and GraphQL. :)

[danrot]

Hey, I've had a quick look at the repo from @gojanpaolo, and it indeed looks similar to what I've been doing... I am using the following query:

// Removed

And the result looks like this:

// Removed

I'll have another closer look soonish and will report back.

[danrot]

Talked to @michaelstaib and he found the issue 🙂 The ExtendObjectType(currently) cannot override existing properties, and my Employee class already has a Absences property defined. The easiest way to solve the issue was to just use UseProjection, which made the entire EmployeeResolvers class obsolete.

PS: @gojanpaolo it would be nice if you could delete the repository you have created again. I am using that example in a classroom situation, and I don't want the students to find an almost finished example easily on the web 🙂

[michaelstaib]

We will change this behavior with 11.1

[ThisNoName]

Well, that is because you are using a single DBContext :)

you need to use pooled db contexts at least with version 11.0 and 11.1. We will teach the execution engine about services that can not be used in parallel with the May release.

Will the parallel setting be keyed/grouped or something? Like when business layer talking to different databases, it makes sense to still allow parallel between different databases. Thanks